FOURTH AMENDMENT TO PURCHASE AGREEMENT

      This  Fourth  Amendment  to  Purchase  Agreement  (the
"Fourth Amendment") dated the 17th day of February, 2004, by
and between AEI REAL ESTATE FUND XVIII LIMITED PARTNERSHIP a
Minnesota limited partnership of 1300 Wells Fargo Place, St.
Paul,  Minnesota  ("Seller") and TEXAS TACO  CABANA,  LP,  a
Texas  limited partnership of 8918 Tesoro Drive, Suite  200,
San Antonio, Texas 78217 ("Buyer").

                          RECITALS

      WHEREAS  Seller  and  Buyer  entered  into  a  certain
Purchase Agreement dated May 21, 2003 covering real property
commonly known as 7339 San Pedro Avenue, San Antonio,  Texas
and  more  particularly  described  therein  (the  "Purchase
Agreement"); and

      WHEREAS by First Amendment to Purchase Agreement dated
July  18,  2003  the  Seller  and  Buyer  extended  the  Due
Diligence Period thirty (30) days to expire August 20, 2003;
and

     WHEREAS by Second Amendment to Purchase Agreement dated
August  12,  2003,  the Seller and Buyer  extended  the  Due
Diligence  Period  sixty (60) days beyond August  20,  2003,
which Due Diligence Period expires October 20, 2003; and

      WHEREAS by Third Amendment to Purchase Agreement dated
October  16,  2003, the Seller and Buyer  extended  the  Due
Diligence   Period  beyond  October  20,  2003,  which   Due
Diligence Period expires February 17, 2004; and

      WHEREAS  Buyer and Seller desire to amend the Purchase
Agreement to extend the Due Diligence Period beyond February
17, 2004; and

     WHEREAS  Buyer and Seller desire to further  amend  the
Purchase  Agreement  to  reduce the Purchase  Price  by  One
Hundred Thousand and 00/100 Dollars ($100,000.00);

      NOW, THEREFORE, for and in consideration of the sum of
ten  and  00/100 Dollars ($10.00) the terms, conditions  and
mutual covenants and agreements contained herein, and  other
good  and valuable consideration the receipt and sufficiency
of  which is hereby acknowledged, Seller and Buyer agree  to
amend the terms of the Purchase Agreement as follows:

     1.   The  introduction and Whereas paragraphs above are
          incorporated into this section by reference as if more
          fully set forth herein.

     2.   All capitalized terms used herein shall have the same
          meaning as ascribed to them in the Purchase Agreement
          unless a contrary meaning is specifically set forth herein.

     3.   Section 6 of the Purchase Agreement is hereby amended
          to extend the Due Diligence Period so that the Due Diligence
          Period shall now expire midnight April 16, 2004. The Due
          Diligence Period may, at Buyer's option, be extended for two
          (2) additional, thirty (30) day periods (each, an "Extension
          Period"), by Buyer providing written notice thereof to
          Seller. If at any time during the Due Diligence Period or
          Extension Period thereof, Buyer, in its sole discretion,
          determines that the Property is not suitable for Buyer's
          intended use, Buyer may terminate this Agreement and obtain
          a full refund of the Deposit together with interest thereon.

     4.   Section 3 of the Purchase Agreement is hereby deleted
          and replaced with the following:

     3.   PURCHASE PRICE. The purchase price  for  this
          Property is $1,645,000 all cash."

     5.   All other dates in the Purchase Agreement that are
          dependent upon the Due Diligence Period shall be calculated
          based on the expiration date for the Due Diligence Period of
          April 16, 2004 (or as may be extended as provided in Section
          6 as amended) all established by this Fourth Amendment.

     6.   Except   as  modified  herein,  all  other  terms,
          conditions,   and   covenants  in   the   Purchase
          Agreement remain in full force and effect.

     IN  WITNESS  WHEREOF, the parties have hereunto  signed
this Fourth Amendment.

                              TEXAS TACO CABANA, LP

                              By: Taco Cabana Management,
                              Inc., a Texas corporation, its
                              general partner

                              By:  /s/ William E Myers
                              Name:    William E Myers
                              Title:   Vice President


                              AEI REAL ESTATE FUND XVIII LIMITED
                              PARTNERSHIP

                              By: AEI Fund Management XVIII,
                              Inc., a Minnesota corporation its
                              general partner

                              By:  /s/ Robert P Johnson
                              Name:    Robert P Johnson
                              Title:   President