
<PAGE>

                                                                   EXHIBIT 10.15

                    SIXTH AMENDMENT TO LEASE AGREEMENT FOR 

                                GREENWAY TOWER


          This Sixth Amendment to Lease Agreement for Greenway Tower is made and
entered into as of the 1st day of February, 1996, by and between GREENWAY TOWER
JOINT VENTURE, a Texas joint venture, as Lessor ("Lessor") and ACE CASH EXPRESS,
INC., a Texas corporation, as Lessee ("Lessee").

                                 W I T N E S S E T H:
                                 ------------------- 

          A.  Reference is made to that certain Office Lease dated October 1,
1987, between Lessor, as lessor, and Lessee, as lessee, as amended by First
Amendment to Lease Agreement for Greenway Tower dated April 29, 1988, Second
Amendment to Lease Agreement for Greenway Tower dated August 24, 1988, Third
Amendment to Lease Agreement for Greenway Tower, Fourth Amendment to Lease
Agreement for Greenway Tower dated January 29, 1991 and Fifth Amendment to Lease
Agreement for Greenway Tower dated June 13, 1994 (as amended, the "Lease"),
pursuant to the terms of which Lessor has leased to Lessee, and Lessee has
leased from Lessor, the premises (the "Premises") designated as Suite 800, being
all of the 8th floor in the office building located at 1231 Greenway Drive,
Irving, Texas, known as "Greenway Tower" (the "Building").

          B.  The Lessor and Lessee desire to amend the Lease as hereinafter set
forth.

                                 AGREEMENT
                                 ---------

          NOW, THEREFORE, in consideration of the premises, and other good and
valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, the parties hereby agree as follows:

          1.  Premises. Effective as of March 1, 1996: (a) the Premises shall be
              --------
expanded to include the space located on the seventh (7th) floor of the Building
as shown on Annex 1 attached hereto, containing approximately 18,618 square feet
            -------
of usable area and approximately 20,294 square feet of rentable area (the
"Expansion Space"); and (b) the Premises shall not include the approximately
1,251 square feet of rentable area shown on Annex 2 attached hereto, being all
                                            -------  
of the space leased by Lessee which is located on the ninth (9th) floor of the
Building (the "Excluded Space"). The Excluded Space shall be surrendered by
Lessee to Lessor in the condition required by the Lease on or prior to February
29, 1996. Lessor and Lessee agree that for all purposes of the Lease, following
the addition of such Expansion Space to the Premises, and the surrender of the
Excluded Space, the Premises will contain approximately 37,162 square feet of
usable area and approximately 40,507 square feet of rentable area.

          2. Base Rent.  The Base Rent payable under the Lease shall be as
             ---------
follows, prorated in the event of a partial month:

                                      -1-
<PAGE>
 
<TABLE>
<CAPTION>

Monthly Base
                                 Rent Installment
                                 ----------------
<S>                              <C>
 
     2/1/96 through 2/29/96            $24,300.43
     3/1/96 through 4/30/96            $44,189.01
     5/1/96 through 4/30/97            $42,194.79
     5/1/97 through 4/30/98            $45,570.38
     5/1/98 through 4/30/99            $48,945.96
     5/1/99 through 4/30/2001          $52,321.54
</TABLE>

which amount shall be payable on or before the first day of each month during
the remaining term of the Lease, without offset, demand, set off or deduction.
Notwithstanding the foregoing, if Lessee has not surrendered possession of the
Excluded Space to Lessor in the condition required by the Lease on or prior to
February 29, 1996, in addition to other amounts payable under the Lease, Lessee
shall pay to Lessor as Base Rent with respect to the Excluded Space until such
time as the Excluded Space is surrendered to Lessor in the condition required by
the Lease the sum of $1,355.25 per month at the same time that installments of
Base Rent are due with respect to the remainder of the Premises.

          3. Term.  The Lease Term is hereby extended to and shall end upon
             ----
April 30, 2001. Lessee shall have no further right to renew or extend the Lease.

          4. Tax and Expense Stop. Effective as of February 1, 1996, the terms
              --------------------
"Tax and Expense Stop", "Tax Stop" and "Expense Stop" as used in the Lease shall
mean the actual amount of Taxes and Operating Expenses, as applicable, incurred
by Lessor in connection with the Property during the calendar year 1995 or 1996,
whichever is greater.

          5. Services.  Article 7 of the Lease is amended to provide that:
             --------

          (a)  Lessor shall provide heat and air-conditioning to the Premises as
               required therein from 7:00 a.m. to 7:00 p.m., Monday through
               Friday, and 8:00 a.m. to 1:00 p.m. on Saturdays, subject to the
               other provisions of the Lease, except that (i) Lessor shall not
               be required to provide such services on Sundays or local, state
               or national holidays; and (ii) Lessor shall provide such services
               during hours other than those stated above upon at least twenty
               four (24) hours prior notice from Lessee to Lessor at the rate of
               $45.00 per hour, per floor, with a two (2) hour minimum, which
               amount shall be payable by Lessee to Lessor within ten (10) days
               following receipt of an invoice therefor;

          (b)  Lessor shall install a separate electric meter in Lessee's
               computer room for the purpose of monitoring electrical usage in
               the computer room. In addition to other sums payable under the
               Lease, Lessee shall pay to Lessor within ten (10) days following
               receipt of an invoice therefor, all charges for electricity
               consumption from the computer room, based upon the actual rate
               charged to Lessor for such usage plus five percent (5%). Lessee
               shall not be required to pay as a part of Operating Expenses with
               respect to the portion of the Premises included within the
               computer room any increases in electrical charges for the
               Building over the amount included in calculating the Expense
               Stop. However, Lessee shall remain obligated to pay increases in

                                      -2-
<PAGE>
 
               connection with the computer room with respect to all other
               components of Operating Expenses; and

          (c)  Lessor shall provide janitorial service to the Premises
               substantially in accordance with the janitorial specifications
               which are set forth on Annex 3 attached hereto.

          6.   Condition of Premises.
               --------------------- 

          (a)  Lessee has inspected and approved the condition of the Expansion
               Space and agrees that the Expansion Space is suitable for
               Lessee's use and occupancy. Lessee acknowledges that Lessor has
               not undertaken and shall not be required to perform any
               modifications, alterations or improvements to the Premises, and
               that, except as provided in this Amendment, all installations and
               improvements now or hereafter placed on the Premises shall be at
               Lessee's cost (and Lessee shall pay ad valorem taxes and
               increased insurance thereon or attributable thereto).

          (b)  Lessee agrees to construct or have constructed within the
               Premises, in accordance with working drawings, plans and
               specifications prepared by Lessee's architect and approved by
               Lessor and Lessee, the improvements which are described in the
               approved plans. All construction by Lessee within the Premises
               shall be subject to the requirements of Annex 4 attached hereto
                                                       -------
               and made a part hereof.

          (c)  Lessor shall remove all debris from the Expansion Space prior to
               delivery of possession of the Expansion Space to Lessee.

          7.   Parking. During the remaining term of the Lease, provided that
               -------
Lessee is not in default in the payment or performance of its obligations under
the Lease: (a) Lessee shall have the nonexclusive right to use, in common with
Lessor and other tenants of the Building, their guests and invitees, of the non-
reserved common automobile parking areas associated with the building at a ratio
of one space for each 280 square feet of rentable area contained within the
Premises; and (b) Lessor agrees to designate a total of twelve (12) reserved
surface parking spaces for use by Lessee (inclusive of the five (5)) reserved
surface parking spaces currently designated for Lessee under the Lease).

          8.   Signage. During the remaining term of the Lease, as long as
               -------
Lessee is not in default thereunder, Lessor agrees, at Lessor's expense, to
place Lessee's name on the Building marquee located on Greenway Drive and on the
Building directory located in the lobby of the Building.

          9.   Representations and Warranties by Lessee. Lessee represents and
               ----------------------------------------
warrants to Lessor that: (i) Lessee has not previously assigned, sublet,
encumbered or otherwise transferred the Lease or Lessee's interest therein, (ii)
this Amendment constitutes a valid and legally binding obligation of Lessee and
is enforceable in accordance with its terms, and (iii) Lessee has the requisite
power and authority to execute and deliver this Amendment, and the consent or
joinder of no other person or entity is required in connection therewith.

          10.  Miscellaneous. Lessor and Lessee agree that the Lease, as
               -------------
modified by this Amendment, sets forth the entire agreement between Lessee and
Lessee with respect to the rental of the Premises and that there are no
statements, representations, agreements or writings which are collateral or
incident to the Lease or the obligations of Lessor or Lessee thereunder, except
as are expressly set forth in writing in the Lease and in this Amendment. Lessee
hereby ratifies and affirms the Lease and each of Lessee's obligations
thereunder and

                                      -3-
<PAGE>
 
confirms that Lessee has no offsets, defenses or counterclaims against Lessor
under or in connection with the Lease. Except as amended hereby, the Lease is
and remains in full force and effect as therein written. The provisions of this
Amendment shall serve to supplement and amend the Lease as set forth herein. In
the event of a conflict between the provisions of this Amendment and the
provisions of the Lease, the provisions of this Amendment shall control.
Capitalized terms which are used herein as defined terms but which are not
otherwise defined shall have the same meaning given to such terms in the Lease.

     EXECUTED as of the day and year first above written.

                              LESSOR:

                              GREENWAY TOWER JOINT VENTURE

                              By:    Independence Development Inc., a Texas
                                     corporation, General Partner
 
                                     By:  /S/ GARY HAMMOND
                                     Name:  Gary Hammond
                                     Title:  Leasing Agent
 
                              LESSEE:

                              ACE CASH EXPRESS, INC.,
                              a Texas corporation
 
                                     By:  /S/ DONALD H. NEUSTADT
                                     Name:  Donald H. Neustadt
                                     Title:  President and Chief Executive
                                              Officer

                                      -4-
<PAGE>
 
                                  EXHIBIT  1

                             WORK LETTER AGREEMENT

          THIS WORK LETTER AGREEMENT IS ATTACHED TO AND FORMS A PART OF THE
SIXTH AMENDMENT TO LEASE AGREEMENT FOR GREENWAY TOWER (THE "AMENDMENT") DATED
FEBRUARY 1, 1996, BETWEEN GREENWAY TOWER JOINT VENTURE, A TEXAS JOINT VENTURE
("LESSOR") AND ACE CASH EXPRESS, INC., A TEXAS CORPORATION ("LESSEE"), MODIFYING
THE LEASE (HEREIN SO CALLED) MORE PARTICULARLY DESCRIBED THEREIN, COVERING THE
PREMISES (HEREIN SO CALLED) COMMONLY KNOWN AS SUITES 700 AND 800 OF THE BUILDING
KNOWN AS GREENWAY TOWER LOCATED AT 1231 GREENWAY DRIVE, IRVING, TEXAS.

          1.  LESSEE'S PLANS. Lessee shall employ an architect approved by
              --------------
Lessor and duly licensed to practice in the State where the Premises are located
("Lessee's Architect"), who shall prepare and submit to the Lessor plans,
specifications and drawings describing Lessee's desired improvements to the
Premises ("Plans"). The Plans shall be subject to the prior written approval of
Lessor. Lessor's approval of such Plans shall not render Lessor liable or
responsible to Lessee or any other party for any defects or deficiencies in such
Plans or any improvements constructed pursuant to the terms thereof. Lessee and
Lessee's Architect shall be solely responsible for compliance with all
applicable legal requirements, including without limitation building and fire
codes.

          2.  CONSTRUCTION. Lessee will cause the leasehold improvements
              ------------
described in the Plans approved by Lessor to be constructed at its cost and
expense in accordance with the Plans ("Lessee's Work"), applicable legal
requirements and the building guidelines set forth on Appendix 1 attached hereto
                                                      ----------
and made a part hereof for all purposes.

          (a) PERMITS. In connection with Lessee's Work, Lessee shall file all
              -------                                                         
drawings, plans and specifications, pay all fees and obtain all permits and
applications from any authorities having jurisdiction; and Lessee shall promptly
obtain a permanent certificate of occupancy and all other approvals required of
Lessee to use and occupy the Premises and to open for business with the public.

          (b) APPROVAL. Prior to the commencement of Lessee's Work, Lessee shall
              --------                                                          
submit to Lessor for Lessor's approval a list of contractors and/or
subcontractors who will perform Lessee's Work or Lessor may, at Lessor's option,
require that the portion of the work involving the heating, ventilating and air
conditioning, electrical, plumbing and sprinkler systems be done by a contractor
and/or subcontractors selected by Lessor (which shall be deemed for purposes of
this Work Letter Agreement to be Lessee's contractor). Lessee or Lessee's
contractors or subcontractors shall be required to obtain from Lessor permission
for using any area outside the Premises for storage, handling or moving
materials and equipment or for parking any vehicles. In addition, Lessee and its
contractors and subcontractors shall comply with Lessor's building guidelines
applicable to construction of Lessee's Work which are set forth on Appendix 1
                                                                   ----------
attached hereto and made a part hereof for all purposes. If any of Lessee's Work
relates to areas or conditions over which Lessor requires sole control, then
Lessor shall have the right at Lessor's discretion to perform (or have Lessor's
contractor perform) such portion of Lessee's Work at Lessee's expense.

          (c) INSURANCE. Lessee and/or Lessee's contractors and subcontractors
              ---------                                                       
shall be required to provide, in addition to the insurance required to be
maintained by Lessee pursuant to the

                                      -5-
<PAGE>
 
Amendment, the following types of insurance and the following minimum amounts,
naming Lessor and any other persons having an interest in the building as
"additional insureds" or "as their interests may appear", issued by companies
and in form and substance approved by Lessor:

               (i) Workman's Compensation coverage with limits of at least
          $500,000.00 for the employer's liability coverage thereunder.

               (ii) All Risk Builders Risk on 100% Completed Value, covering
          damage to the construction and improvements to be made by Lessee with
          100% coinsurance protection.

               (iii)  Automobile Liability coverage with bodily injury limits of
          at least $1,000,000.00 per accident and $500,000.00 accident for
          property damage.

               (iv) Other insurance reasonably required by Lessor.

Original or duplicate policies for all of the foregoing insurance shall be
delivered to Lessor before Lessee's Work is started and before any contractor's
or subcontractor's equipment is moved on to any part of the Premises.

          (d) LIABILITY DURING CONSTRUCTION. Lessee hereby assumes any and all
              -----------------------------                                   
liability arising out of or relating to Lessee's Work or to the Premises after
the date hereof, including any liability arising out of statutory or common law
for any and all injuries to or death of any and all persons (including, without
limitation, Lessee's contractors and subcontractors and their employees) and any
liability for any and all damage to property caused by, or resulting from, or
arising out of any act or omission on the part of the Lessee, Lessee's
contractors and Lessee's or their subcontractors or employees in the performance
of Lessee's Work, and Lessee further agrees to defend, indemnify and save
harmless Lessor from and against all damages, claims, costs, liabilities, losses
and/or expenses (including legal fees and expenses) arising out of or related to
Lessee's Work, including without limitation any and all such injuries, death
and/or damage. Lessee agrees to insure the foregoing assumed contractual
liability in its liability policies and the original or duplicate original of
said policy that Lessee will deliver to Lessor shall expressly include said
contractual liability coverage.

          (e) REMOVAL DURING CONSTRUCTION. Contractors and/or subcontractors
              ---------------------------                                   
participating in the Lessee's Work shall be required to keep the Premises and
adjacent areas in a neat and clean condition and to remove and dispose of, as
frequently as Lessor may direct, all debris and rubbish caused by, or resulting
from the work and upon completion, to remove all temporary structures, surplus
materials, debris and rubbish of whatever kind remaining on any part of the
Premises or in proximity thereto that was brought in or created by the
performance of Lessee's Work. If at any time Lessee's contractors and
subcontractors shall neglect, refuse, or fail to remove any debris, rubbish, or
surplus materials within twenty-four (24) hours after written notice to Lessee,
Lessor may remove the same at Lessee's expense.

          (f) CHANGES. All changes to the Plans shall be subject to Lessor's
              -------                                                       
prior written approval.

          (g) AFFIDAVITS. Lessee shall cause to be filed and/or recorded such
              ----------                                                     
affidavits as Lessor requests regarding Lessee's Work, including without
limitation an affidavit of commencement of Lessee's

                                      -6-
<PAGE>
 
Work and an affidavit of completion of Lessee's Work on the dates required by
law to give proper effect thereto, or if requested by Lessor, on the dates
specified by Lessor.

     3.   Removal of Lessee's Work at expiration or termination of Lease.
          -------------------------------------------------------------- 
Lessee's Work (including any Changes) shall be the property of Lessor and shall
remain upon and be surrendered with the Premises upon the expiration of the
Lease term; provided, that at Lessor's option, Lessee shall, at Lessee's sole
cost and expense, remove all of Lessee's Work from the Premises upon expiration
or termination of the Lease, and restore any damage to the Premises resulting
therefrom.

     4.   CONFLICTS AND CONFORMITY WITH LEASE. Any rights and obligations of
          -----------------------------------                               
Lessor and Lessee relative to any matter not stated in this Work Letter
Agreement shall be governed by the Lease. If there shall be any conflict between
this Work Letter Agreement and the Lease, the provisions of this Work Letter
Agreement shall prevail. As used herein, all capitalized terms not defined
herein shall have the same meaning as defined in the Lease.

                                      -7-
<PAGE>
 
     5.   ALLOWANCE.
          --------- 

          (a)  Lessee's Work shall be done at Lessee's expense, including
building permit fees, other fees, architectural and engineering expenses and
other expenses relating to Lessee's Work. However, Lessor shall allow Lessee a
finish-out allowance of $185,810.00 (the "Allowance") to be applied toward
payment of actual out of pocket costs incurred by Lessee in connection with the
completion of Lessee's Work; subject to the following: (i) Lessor shall not be
required to advance any portion of the Allowance with respect to any invoice or
request for disbursement submitted by Lessee to Lessor after February 28, 1997;
and (ii) Lessee shall be entitled to use up to but not in excess of $30,000.00
out of the Allowance for costs associated with the acquisition and installation
of data cabling within the Premises.  Except for the portion of the Allowance
which may be used for data cabling as set forth in clause (ii) of the preceding
sentence, the proceeds of the Allowance shall be used solely for payment of
eligible costs incurred in constructing the permanent leasehold improvements
described in the Plans approved by Lessor, and Lessor shall not be required to
advance any portion of the Allowance for any moving, telephone, equipment or
other expenses incurred by Lessee in connection with the Premises.  Lessee
understands that if the cost of Lessee's Work, including without limitation any
changes in Lessee's Work, exceeds the Allowance, then Lessee shall be solely
responsible for all such costs in excess of the Allowance. The Allowance shall
be due and payable to Lessee only after lien-free final completion of Lessee's
Work in accordance with the Plans, receipt by Lessee of all necessary approvals
to operate its business at the Premises, completion by Lessor of a final
inspection and approval of Lessee's Work, and receipt by Lessor of:  proof that
all bills in connection with Lessee's Work have been paid in full and all
persons or entities with the right to file a lien in connection therewith have
finally waived and released their lien rights in connection therewith in a
manner satisfactory to Lessor; a copy of Lessee's certificate of occupancy; an
original Affidavit of Total Release and Bills Paid in form acceptable to Lessor
signed by Lessee and by the general contractor, indicating that all
subcontractors and suppliers have been paid, and accompanied by copies of the
invoices referred to therein; and a copy of "as-built" plans of finish-out.

          (b) If the actual construction costs are less than the Allowance, then
Lessee shall not be entitled to any portion of the unexpended Allowance, which
shall belong to Lessor.
 

                                      -8-
