FIRST AMENDMENT TO NET LEASE AGREEMENT


     THIS AMENDMENT TO NET LEASE AGREEMENT, made and entered into
effective  as  of  the 28 day of April, 2003 by and  between  AEI
Income & Growth Fund XXI Limited Partnership ("Fund XXI"),  whose
corporate general partner is AEI Fund Management XXI, Inc., whose
address  is  1300 Wells Fargo Place, 30 East Seventh Street,  St.
Paul,  Minnesota  55101 ("Lessor")(fax #651 227  7705),  and  SFG
Farmington-I  Limited  Partnership, a Texas limited  partnership,
whose  address is 6001 Indian School NE, Suite 320,  Albuquerque,
NM 87110 ("Lessee") (fax # 505 881 9700);

                          WITNESSETH:

     WHEREAS, Lessor is the fee owner of a certain parcel of real
property and improvements located at Farmington, New Mexico,  and
legally  described in Exhibit "A", which is attached  hereto  and
incorporated  herein by reference and shall  substitute  for  the
Exhibit  A  heretofore attached to the Lease (as defined  below);
and

       WHEREAS,   Lessee   has  constructed  the   building   and
improvements  (together  the "Building")  on  the  real  property
described  in  Exhibit "A", which Building is  described  in  the
plans and specifications heretofore submitted to Lessor; and

     WHEREAS,  Lessee and Lessor have entered into  that  certain
Net   Lease  Agreement  dated  October  31,  2002  (the  "Lease")
providing for the lease of said real property and Building  (said
real property and Building hereinafter referred to as the "Leased
Premises"),  from  Lessor upon the terms and  conditions  therein
provided in the Lease;

     NOW,  THEREFORE,  in  consideration  of  the  Rents,  terms,
covenants, conditions, and agreements hereinafter described to be
paid, kept, and performed by Lessee, including the completion  of
the  Building  and  other  improvements constituting  the  Leased
Premises, Lessee and Lessor do hereby agree to amend the Lease as
follows:

1.    Article 2(A) and (B) of the Lease shall henceforth read  as
follows:

ARTICLE 2.     TERM

     (A)   The  term of this Lease ("Term") shall be  the  period
commencing  October  31,  2002  ("Occupancy  Date")  through  the
effective  date  hereof,  plus  twenty  (20)  consecutive  "Lease
Years", as hereinafter defined, commencing on the effective  date
hereof, with the contemplated initial term hereof ending  on  May
31, 2023.                            .

   (B)  The  first full Lease Year shall commence on the date  of
this  First  Amendment and continue through May  31,  2004.  Each
Lease  Year  after  the first Lease Year shall  be  a  successive
period of twelve (l2) calendar months.


2.   Article 4(A) of the Lease shall henceforth read as follows:

ARTICLE 4.  RENT PAYMENTS

  (A)  Annual Rent Payable for the first  Lease Year:  Lessee shall
       pay to Lessor an annual Base Rent of $231,000,  which amount
       shall be payable in advance on the first day of  each  month
       in equal monthly installments of $19,250 to Fund XXI. If the
       first  day of  the Lease Term is  not  the  first  day of  a
       calendar month,  then  the  monthly  Rent  payable for  that
       partial   month  shall  be  a prorated portion of the  equal
       monthly installment of Base Rent.



3.   Lessee has accepted delivery of the Leased Premises and  has
     entered into occupancy thereof;

4.   Lessee  has fully inspected the  Premises and found the  same
     to be as required by the Lease, in good order and repair, and
     all conditions under the Lease to be performed  by the Lessor
     have been satisfied;

5.   As  of this date, the Lessor is not in default  under any  of
     the terms, conditions, provisions or agreements of  the Lease
     and  the  undersigned  has  no  offsets,  claims  or defenses
     against the Lessor with respect to the Lease.

6.   Exhibit B to the Lease shall be as attached hereto.

7.   This  Agreement  may  be executed in  multiple  counterparts,
     each of which shall be deemed an original and  all  of  which
     shall constitute one and the same instrument.

IN  WITNESS  WHEREOF, Lessor and Lessee have  respectively  signed
and sealed this Lease as of the day and year  first above written.

LESSEE:        SFG FARMINGTON-I LIMITED PARTNERSHIP

                              By:  SFG FNM GP-1, Inc.

                              By: /s/ Mark G. Day
                                      Mark G. Day [Print Name]
                              Its: President

LESSOR:

               AEI INCOME & GROWTH FUND XXI LIMITED PARTNERSHIP

               By:  AEI FUND MANAGEMENT XXI, INC., a Minnesota corporation
                    Its corporate general partner


                    By:  /s/ Robert P. Johnson
                             Robert P. Johnson, President