
<PAGE>   1
                                                                   EXHIBIT 10.43

THE SECURITIES REPRESENTED HEREBY AND ISSUABLE UPON EXERCISE HEREOF HAVE NOT
BEEN REGISTERED UNDER THE SECURITIES ACT OF 1933, AS AMENDED (THE "ACT"), OR
UNDER THE SECURITIES LAWS OF ANY STATE. ALL SUCH SECURITIES ARE SUBJECT TO
RESTRICTIONS ON TRANSFERABILITY AND RESALE AND MAY NOT BE TRANSFERRED OR RESOLD
EXCEPT AS PERMITTED UNDER THE ACT AND THE APPLICABLE STATE SECURITIES LAWS,
PURSUANT TO REGISTRATION OR EXEMPTION THEREFROM. THE ISSUER OF SUCH SECURITIES
MAY REQUIRE AN OPINION OF COUNSEL IN FORM AND SUBSTANCE REASONABLY SATISFACTORY
TO THE ISSUER TO THE EFFECT THAT ANY PROPOSED TRANSFER OR RESALE IS IN
COMPLIANCE WITH THE ACT AND ANY APPLICABLE STATE SECURITIES LAWS.

            Void after 5:00 p.m. New York Time, on __________, 1998.

                             BRANDYWINE REALTY TRUST

          Warrant Agreement for the Purchase of Shares of Common Stock


No. 1                                                            400,000 Shares

                  FOR VALUE RECEIVED, BRANDYWINE REALTY TRUST, a Maryland real
estate investment trust (the "Company"), with its principal office at 16 Campus
Boulevard, Suite 150, Newtown Square, Pennsylvania 19073, hereby certifies that
RAI Real Estate Advisers, Inc. as voting trustee of a voting trust dated as of
November 6 ,1996 or its assigns (the "Holder") is entitled, subject to the
provisions of this Warrant, to purchase from the Company, at any time before
5:00 p.m. (Eastern Time) on ____________ __, 1998 (the "Expiration Date"), the
number of fully paid and nonassessable common shares of beneficial interest of
the Company (the "Common Stock") set forth above, subject to adjustment as
hereinafter provided.

                  The Holder may purchase such number of shares of Common Stock
at a purchase price per share (as appropriately adjusted pursuant to Section 6,
Section 8 or Section 9 hereof) of Eight Dollars and 50/100 Cents ($8.50) (the
"Exercise Price"). As provided in Section 6(j), the term "Common Stock" shall
mean the aforementioned Common Stock of the Company, together with any other
equity securities that may be issued by the Company in addition thereto or in
substitution therefor as provided herein.

                  The number of shares of Common Stock to be received upon the
exercise of this Warrant and the price to be paid for a share of Common Stock
are subject to adjustment from time to time as hereinafter set forth. The shares
of Common Stock deliverable upon such


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exercise, as adjusted from time to time, are hereinafter sometimes referred to
as "Warrant Shares."

                  Section 1. Exercise of Warrant. (a) This Warrant may be
exercised in whole or in part on any business day (the "Exercise Date")
occurring from and after the date hereof and on or before the Expiration Date by
presentation and surrender hereof to the Company at its principal office at the
address set forth in the initial paragraph hereof or at the office of its stock
transfer or warrant agent, if any, (or at such other address as the Company may
hereafter notify the Holder in writing) with the Purchase Form annexed hereto
duly executed and accompanied by proper payment of the Exercise Price in lawful
money of the United States of America in the form of a check, subject to
collection, for the number of Warrant Shares specified in the Purchase Form. If
this Warrant should be exercised in part only, the Company shall, upon surrender
of this Warrant, execute and deliver a new Warrant evidencing the rights of the
Holder thereof to purchase the balance of the Warrant Shares purchasable
hereunder. Upon receipt by the Company of this Warrant and such Purchase Form,
together with proper payment of the Exercise Price, at such office, the Holder
shall be deemed to be the holder of record of such Warrant Shares,
notwithstanding that the stock transfer books of the Company shall then be
closed or that certificates representing such Warrant Shares shall not then be
actually delivered to the Holder, which certificates shall be delivered to the
Holder within two (2) business days following the Company's receipt of the
Warrant together with the aforesaid Purchase Form and payment. The Company shall
pay any and all documentary stamp or similar issue or transfer taxes payable in
respect of the issue or delivery of the Warrant Shares.

                  (b) In addition to and without limiting the rights of the
Holder under any other terms set forth herein, the Holder shall have, upon
written request by the Holder delivered or transmitted to the Company together
with this Warrant, the right (the "Conversion Right") to require the Company to
convert this Warrant into shares of Common Stock as follows: upon exercise of
the Conversion Right, the Company shall deliver to the Holder (without payment
by the Holder of any Exercise Price) that number of shares of Common Stock that
is equal to the quotient obtained by dividing (x) the value of this Warrant at
the time the Conversion Right is exercised (determined by subtracting the
aggregate Exercise Price in effect immediately prior to the exercise of the
Conversion Right from the aggregate current market price (determined as provided
in Section 11 below) of the shares of Common Stock issuable upon exercise of
this Warrant immediately prior to the exercise of the Conversion Right) by (y)
the current market price of one share of Common Stock (determined as provided in
Section 11 below) immediately prior to the exercise of the Conversion Right.

                  The Conversion Right referred to above may be exercised by the
Holder by surrender of this Warrant at the principal office of the Company or at
the offices of its stock transfer or warrant agent, if any, together with a
written statement specifying that the Holder thereby intends to exercise the
Conversion Right. Certificates representing shares of Common Stock issuable upon
exercise of the Conversion Right shall be delivered to the Holder within two (2)
business days following the Company's receipt of this Warrant together with the
aforesaid written statement.


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                  Section 2. Reservation of Shares. The Company shall reserve at
all times for issuance and delivery upon exercise of this Warrant all shares of
its Common Stock or other shares of beneficial interest of the Company from time
to time issuable upon exercise of this Warrant. All such shares shall be duly
authorized and, when issued upon the exercise of the Warrant in accordance with
the terms hereof, shall be validly issued, fully paid and nonassessable, free
and clear of all taxes, liens, security interests, charges and other
encumbrances or restrictions (other than restrictions pursuant to applicable
federal and state securities laws) and free and clear of all preemptive rights.
If the Common Stock is listed on any national securities exchange or The Nasdaq
Stock Market, the Company shall also list the shares issuable upon exercise of
the Warrant on such exchange, subject to notice of issuance, or include the
shares issuable upon exercise of this Warrant in the listing of its Common Stock
on The Nasdaq Stock Market, as the case may be.

                  Section 3. Fractional Interest. The Company will not issue a
fractional share of Common Stock or scrip upon any exercise or conversion of
this Warrant. Instead, the Company shall issue the next highest number of whole
shares of Common Stock.

                  Section 4. Exchange, Transfer, Assignment or Loss of Warrant.

                  (a) The Holder of this Warrant may not transfer or assign its
interest in this Warrant, or any of the Warrant Shares, in whole or in part,
unless, prior to any such transfer, the transferee agrees in writing, in form
and substance satisfactory to the Company, to be bound by the terms of this
Agreement and provides the Company with an opinion of counsel in such form
reasonably acceptable to the Company, that such transfer would not be in
violation of the Act or any applicable state securities laws.

                  (b) Subject to the provisions of subsection (a) above and
Section 10, upon surrender of this Warrant to the Company or its stock transfer
agent or warrant agent, accompanied by the Assignment Form annexed hereto duly
executed and funds sufficient to pay any transfer tax, the Company shall,
without charge, execute and deliver a new Warrant or Warrants in the name of the
assignee or assignees named in such instrument of assignment and, if the
Holder's entire interest is not being assigned, in the name of the Holder, and
this Warrant shall promptly be canceled.

                  (c) This Warrant may be divided by or combined with other
Warrants which carry the same rights upon presentation hereof at the principal
office of the Company or at the office of its stock transfer or warrant agent,
if any, together with a written notice specifying the names and denominations in
which new Warrants are to be issued and signed by the Holder hereof. The term
"Warrant" as used herein includes any warrants into which this Warrant may be
divided or exchanged.

                  (d) Upon receipt of evidence satisfactory to the Company of
the loss, theft, destruction or mutilation of this Warrant, and (in the case of
loss, theft or destruction) of indemnification reasonably satisfactory to the
Company, and upon surrender and cancellation of


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this Warrant, if mutilated, the Company shall execute and deliver a new Warrant
of like tenor and date registered in the Holder's name representing the number
of shares purchasable under the original Warrant. Any such new Warrant executed
and delivered shall constitute an additional contractual obligation of the
Company, whether or not the original Warrant shall be at any time enforceable by
anyone.

                  Section 5. Rights of the Holder. The Holder shall not, by
virtue hereof, be entitled to any rights of a shareholder in the Company, either
at law or equity, and the rights of the Holder are limited to those set forth in
this Warrant.

                  Section 6. Adjustment of Exercise Price and Number of Shares.
The number and kind of securities purchasable upon the exercise of this Warrant
and the Exercise Price shall be subject to adjustment from time to time upon the
occurrence of certain events, as follows:

                  (a) Adjustment for Change in Beneficial Interest. If at any
time after November 6, 1996, the Company:

                           (i) pays a dividend or makes a distribution on its
                           Common Stock in shares of its Common Stock;

                           (ii) subdivides its outstanding shares of Common
                           Stock into a greater number of shares;

                           (iii) combines its outstanding shares of Common Stock
                           into a smaller number of shares;

                           (iv) makes a distribution on its Common Stock in
                           shares of its beneficial interest other than Common
                           Stock; or

                           (v) issues by reclassification of its Common Stock
                           any shares of its beneficial interest;

then the Exercise Price in effect (and the number of Warrant Shares and other
securities, if any, issuable upon exercise of this Warrant) immediately prior to
such action shall be adjusted so that the Holder may receive upon exercise of
the Warrant, and payment of the same aggregate consideration, the number of
shares of beneficial interest of the Company which the Holder would have owned
immediately following such action if the Holder had exercised the Warrants
immediately prior to such action.

                  The adjustment shall become effective immediately after the
record date in the case of such a dividend or distribution, and immediately
after the effective date in the case of a subdivision, combination or
reclassification.


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                  (b) Adjustment for Other Distributions. If at any time after
November 6, 1996, the Company distributes to all holders of its Common Stock any
of its assets or debt securities, the Exercise Price following the record date
for such distribution shall be adjusted in accordance with the following
formula:

                                             M-F
                                   E' = E x -----
                                              M

where:            E'       =        the adjusted Exercise Price.

                  E        =        the then current Exercise Price immediately
                                    prior to the adjustment.

                  M        =        the current market price (determined as
                                    provided in Section 11 below) per share of
                                    Common Stock on the record date of the
                                    distribution.

                  F        =        the aggregate fair market value
                                    (determined in such reasonable manner as may
                                    be prescribed in good faith by the Board of
                                    Trustees of the Company) on the record date
                                    of the distribution of the assets or debt
                                    securities divided by the number of
                                    outstanding shares of Common Stock.

                  The adjustment shall be made successively whenever any such
distribution is made and shall become effective immediately after the record
date for the determination of shareholders entitled to receive the distribution
or the effective date of such issuance, as applicable. Notwithstanding the
formula above, in no event shall the adjusted Exercise Price be less than zero.
In the event that such distribution or issuance is not actually made, the
Exercise Price shall again be adjusted to the Exercise Price as determined
without giving effect to the calculation provided hereby.

                  This subsection does not apply to ordinary quarterly cash
dividends or cash distributions paid out of consolidated current or retained
earnings as shown on the books of the Company and paid in the ordinary course of
business.

                  (c) Deferral of Issuance or Payment. In any case in which an
event covered by this Section 6 shall require that an adjustment in the Exercise
Price be made effective as of a record date, the Company may elect to defer
until the occurrence of such event (i) issuing to the Holder, if this Warrant is
exercised after such record date, the shares of Common Stock and other
beneficial interest of the Company, if any, issuable upon such exercise over and
above the shares of Common Stock or other beneficial interest of the Company, if
any, issuable upon such exercise on the basis of the Exercise Price in effect
prior to such adjustment, and (ii) paying to the Holder by check any amount in
lieu of the issuance of fractional shares pursuant to Section 11.


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                  (d) When No Adjustment Required. No adjustment need be made
for a change in the par value of the Common Stock.

                  (e) Notice of Certain Actions. In the event that:

                           (i) the Company shall authorize the issuance to all
holders of its Common Stock of rights, warrants, options or convertible
securities to subscribe for or purchase shares of its Common Stock, or of any
other subscription rights, warrants, options or convertible securities; or

                           (ii) the Company shall authorize the distribution to
all holders of its Common Stock of evidences of its indebtedness or assets
(other than dividends paid in or distributions of the Company's beneficial
interest for which the Exercise Price shall have been adjusted pursuant to
subsection (a) of this Section 6) or cash dividends or cash distributions
payable out of consolidated current or retained earnings as shown on the books
of the Company and paid in the ordinary course of business); or

                           (iii) the Company shall authorize any capital
reorganization or reclassification of the Common Stock (other than a subdivision
or combination of the outstanding Common Stock and other than a change in par
value of the Common Stock) or any consolidation or merger to which the Company
is a party and for which approval of any shareholders of the Company is required
(other than a consolidation or merger in which the Company is the continuing
corporation and that does not result in any reclassification or change of the
Common Stock outstanding), or the conveyance or transfer of the properties and
assets of the Company as an entirety or substantially as an entirety; or

                           (iv) the Company is the subject of a voluntary or
involuntary dissolution, liquidation or winding-up procedure; or

                           (v) the Company proposes to take any action (other
than actions of the character described in subsection (a) of this Section 6)
that would require an adjustment of the Exercise Price pursuant to this Section
6;

then the Company shall cause to be mailed by first-class mail to the Holder, at
least ten (10) days prior to the applicable record or effective date, a notice
stating (x) the date as of which the holders of Common Stock of record to be
entitled to receive any such rights, warrants or distributions are to be
determined, or (y) the date on which any such consolidation, merger, conveyance,
transfer, dissolution, liquidation or winding-up is expected to become
effective, and the date as of which it is expected that holders of Common Stock
of record shall be entitled to exchange their shares of Common Stock for
securities or other property, if any, deliverable upon such reorganization,
reclassification, consolidation, merger, conveyance, transfer, dissolution,
liquidation or winding-up.


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                  (f) No Adjustment Upon Exercise of Warrants. No adjustments
shall be made under any Section herein in connection with the issuance of
Warrant Shares upon exercise of the Warrants.

                  (g) Common Stock Defined. The term "Common Stock" shall
include any equity securities of any class of the Company hereinafter authorized
which shall not be limited to a fixed sum or percentage in respect of the right
of the holders thereof to participate in dividends, or to participate in
distributions of assets upon the voluntary or involuntary liquidation,
dissolution or winding up of the Company. However, subject to the provisions of
Section 8 hereof, shares issuable upon exercise hereof shall include only shares
of the class designated as Common Stock of the Company as of the date hereof or
shares of any class or classes resulting from any reclassification or
reclassifications thereof or as a result of any corporate reorganization as
provided for in Section 8 hereof.

                  (h) Warrants Issued After Adjustments. Irrespective of any
adjustments in the Exercise Price or the number or kind of Warrant Shares
purchasable upon exercise of this Warrant, Warrants theretofore or thereafter
issued may continue to express the same price and number and kind of shares as
are stated in the similar warrants initially issuable pursuant to this
Agreement.

                  Section 7. Officers' Certificate. Whenever the Exercise Price
shall be adjusted as required by the provisions of Section 6, the Company shall
forthwith file in the custody of its Secretary or an Assistant Secretary at its
principal office an officers' certificate showing the adjusted Exercise Price
determined as herein provided, setting forth in reasonable detail the facts
requiring such adjustment and the manner of computing such adjustment. Each such
officers' certificate shall be signed by the Chairman, President or Chief
Financial Officer of the Company and by the Secretary or any Assistant Secretary
of the Company. A copy of each such officers' certificate shall be promptly
mailed, by certified mail, to each holder of a Warrant and the original shall be
made available at all reasonable times for inspection by any other holder of a
Warrant executed and delivered pursuant to Section 4 hereof.

                  Section 8. Reclassification, Reorganization, Consolidation or
Merger. In the event of any reclassification, capital reorganization or other
change of outstanding shares of Common Stock of the Company (other than a
subdivision or combination of the outstanding Common Stock and other than a
change in the par value of the Common Stock) or in the event of any
consolidation or merger of the Company with or into another person or entity
(other than a merger in which the Company is the continuing person or entity and
that does not result in any reclassification, capital reorganization or other
change of outstanding shares of Common Stock of the class issuable upon exercise
of this Warrant) or in the event of any sale, lease, transfer or conveyance to
another person or entity of the property and assets of the Company as an
entirety or substantially as an entirety, the Company shall, as a condition
precedent to such transaction, cause effective provisions to be made so that the
Holder shall have the right thereafter, by exercising this Warrant, to purchase
the kind and amount of shares of beneficial interest and other securities and
property (including cash) receivable upon such reclassification,


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capital reorganization and other change, consolidation, merger, sale or
conveyance by a holder of the number of shares of Common Stock that might have
been received upon exercise of this Warrant immediately prior to such
reclassification, capital reorganization, change, consolidation, merger, sale or
conveyance. Any such provision shall include provisions for adjustments in
respect of such shares of beneficial interest and other securities and property
that shall be as nearly equivalent as may be practicable to the adjustments
provided for in this Warrant. The foregoing provisions of this Section 8 shall
similarly apply to successive reclassifications, capital reorganizations and
changes of shares of Common Stock and to successive consolidations, mergers,
sales or conveyances. In the event that in connection with any such capital
reorganization, or classification, consolidation, merger, sale or conveyance,
additional shares of Common Stock shall be issued in exchange, conversion,
substitution or payment, in whole or in part, for, or of, a security of the
Company other than Common Stock, any such issue shall be treated as an issue of
Common Stock covered by the provisions of Section 6 hereof.

                  Section 9. Duty to Make Fair Adjustments in Certain Cases. If
any event occurs as to which, in the reasonable opinion of either the Board of
Trustees of the Company or a majority of the holders of the warrants then
outstanding under this Warrant, the Warrants issued to the Turkey Vulture Fund
XIII, Ltd. on June 21, 1996, the Warrants issued to Safeguard on August 22, 1996
and any warrants issued upon repayment of unsecured debt issued to or held by
Osborne (collectively, the "Other Warrants"), the provisions of Section 6 and
Section 8 hereof are not strictly applicable or, if strictly applicable, would
not fairly protect the purchase rights of the holders of such warrants in
accordance with the essential intent and principles of such provisions, then the
Board of Trustees of the Company and a majority of the holders of the warrants
then outstanding under this Warrant and the Other Warrants shall mutually agree
upon an adjustment in the application of such provisions, in accordance with
such essential intent and principles, so as to protect such purchase rights as
aforesaid.

                  Section 10. Transfer to Comply with the Securities Act of
1933; Registration Rights.


                  (a) No sale, transfer, assignment, hypothecation or other
disposition of this Warrant or of the Warrant Shares shall be made if such sale,
transfer, assignment, hypothecation or other disposition would result in a
violation of the Act, or any state securities laws. Upon exercise of this
Warrant, the Holder shall, if requested by the Company, confirm in writing, in a
form reasonably satisfactory to the Company, that the shares of Common Stock so
purchased are being acquired solely for the Holder's own account, and not as a
nominee thereof, for investment, and not with a view toward distribution or
resale, except as permitted by the Act, and shall provide such other information
to the Company as the Company may reasonably request. Any Warrant and any
Warrants issued upon substitution for, or upon assignment or transfer of this
Warrant, as the case may be, and all shares of Common Stock issued upon exercise
hereof or conversion thereof shall bear a legend (in addition to any legend
required by state securities laws) in substantially the form set forth on the
first page of this Warrant, unless and until such securities have been
transferred pursuant to an effective registration statement


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under the Act or may be freely sold to the public pursuant to Rule 144 (or any
successor rule thereto) or otherwise.

                  (b) The Holder and any transferee of the Warrant or the
Warrant Shares issuable hereunder shall have the right to require the Company to
register the Warrant Shares with the Securities and Exchange Commission for
resale as provided in the Registration Rights Agreement of even date herewith by
and between the Holder and the Company.

                  Section 11. Current Market Price. The "current market price"
of a share of Common Stock for purposes of this Agreement shall be determined as
follows:

                  (a) If the Common Stock is listed on a national securities
exchange or admitted to unlisted trading privileges on such exchange or listed
for trading on The Nasdaq Stock Market, the current market price shall be the
last reported sale price of the Common Stock on such exchange or system on the
last business day prior to the date of exercise of this Warrant, or if no such
sale is made on such day, the average of the closing bid and asked prices of the
Common Stock for such day on such exchange or system; or

                  (b) If the Common Stock is not so listed or admitted to
unlisted trading privileges, the current market price shall be the average of
the last reported bid and asked prices reported by the National Quotation
Bureau, Inc., on the last business day prior to the date of exercise of this
Warrant; or

                  (c) If the Common Stock is not so listed or admitted to
unlisted trading privileges and bid and asked prices are not so reported, the
current market price per share shall be an amount, not less than 90% of the book
value per share of the Common Stock as at the end of the most recent fiscal year
of the Company ending prior to the date of the exercise of this Warrant,
determined in such reasonable manner as may be prescribed in good faith by the
Board of Trustees of the Company.

                  Section 12. Modification and Waiver. Neither this Warrant nor
any term hereof may be changed, waived, discharged or terminated other than by
an instrument in writing signed by the Company and by the Holder.

                  Section 13. Notices. Any notice, request or other document
required or permitted to be given or delivered to the Holder or the Company
shall be delivered or shall be sent by certified mail, postage prepaid, or by
overnight courier to each such holder at its address as shown on the books of
the Company or to the Company at the address indicated therefor in the first
paragraph of this Warrant.

                  Section 14. Descriptive Headings and Governing Law. The
description headings of the several sections and paragraphs of this Warrant are
inserted for convenience only and do not constitute a part of this Warrant. This
Warrant shall be construed and enforced in


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accordance with, and the rights of the parties shall be governed by, the laws of
the State of Maryland.

                  Section 15. No Impairment. The Company will not knowingly
avoid or seek to avoid the observance or performance of any of the terms to be
observed or performed hereunder by it, but will at all times in good faith
assist in the carrying out of all of the provisions of this Warrant.

                  Section 16. Non-Recourse. No recourse shall be had for any
obligation of the Company hereunder, or for any claim based thereon or otherwise
in respect thereof, against any past, present or future trustee, shareholder,
officer or employee of the Company, whether by virtue of any statute or rule of
law, or by the enforcement of any assessment or penalty or otherwise, all such
other liability being expressly waived and released by each other party hereto.

                  IN WITNESS WHEREOF, the Company has duly caused this Warrant
to be signed by its duly authorized officer and to be dated as of ______________
__, 1996.

                                       BRANDYWINE REALTY TRUST



                                       By:
                                          -----------------------------------
                                          Gerard H. Sweeney, President


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                                  PURCHASE FORM


                                                     Dated: ____________________

                  The undersigned hereby irrevocably elects to exercise the
within Warrant to purchase _____________ shares of Common Stock and hereby makes
payment of ___________________________ in payment of the exercise price thereof.



                                               Signature________________________


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                                 ASSIGNMENT FORM


                                                     Dated: ____________________


         FOR VALUE RECEIVED,__________________ hereby sells, assigns and
transfers unto _______________________ (the "Assignee"), 
                    (please type or print in block letters)

________________________________________________________________________________
                                (insert address)

its right to purchase up to _______________ shares of Common Stock represented
by this Warrant and does hereby irrevocably constitute and appoint
_______________________________ Attorney, to transfer the same on the books of
the Company, with full power of substitution in the premises.



                                               Signature________________________


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