<PAGE>
 
                                                                   Exhibit 10.13

                         MASTER AGREEMENT NO. MD01546



May 8, 1996

Mr. John Ballard
Home, Inc.
6836 Austin Center Blvd., Suite 280
Austin, TX 78731

Dear Mr. Ballard:

This letter shall constitute the master agreement ("Master Agreement") between
the Federal National Mortgage Association ("Fannie Mae") and Home, Inc. (the
"Lender") to enter into one or more transactions for the sale by the Lender and
purchase by Fannie Mae of residential mortgage loans ("Mortgages"). The
obligations of the Lender and Fannie Mae regarding each such transaction shall
be governed by the terms and conditions contained herein (including Exhibit 1
                                                                    ---------
and each of the Attachments attached hereto and incorporated herein by
reference) and by the terms and conditions of the applicable Fannie Mae purchase
program ("Program").

The Lender will sell to Fannie Mae, beginning on the Effective Date and ending
on the Expiration Date (as those terms are defined in Exhibit 1), Mortgages with
                                                      -----------               
an aggregate outstanding principal balance equal to the Agreed Amount (as
defined in Exhibit 1) under one or more of the following Programs:
           ----------                                             

(a) Fannie Mae's Mortgage-Backed Securities Program, under terms mutually
acceptable to the Lender and Fannie Mae and which will be set forth herein and
under the applicable MBS Pool Purchase Contract obtained through the Lender's
Fannie Mae lead regional office, or

(b) Fannie Mae's Negotiated Transaction Program for cash purchase under terms
mutually acceptable to Lender and Fannie Mae and which will be set forth herein
and when applicable, under a special commitment obtained through the Lender's
Fannie Mae lead regional office, or

(c) Fannie Mae's Standard Portfolio (cash) purchase commitment Program, under
the then-current terms and conditions applying thereto.

If the Agreed Amount is not sold to Fannie Mae prior to the Expiration Date,
the Lender shall pay Fannie Mae the Back-end Buyout Fee, as indicated in Exhibit
                                                                         -------
1. (The undelivered and uncommitted portion of the Agreed Amount shall be the
--                                                                           
difference between (a) the Agreed Amount (taking into account the minus 5.00%
delivery tolerance, as specified in Exhibit 1), and (b) a sum equal to the
                                    -----------                           
aggregate outstanding principal balance of Mortgages (for each Mortgage, as of
the time of sale of the Mortgage) that the Lender has sold to Fannie Mae under
this Master Agreement, plus the principal balance of Mortgages that the Lender
is still obligated to sell under any existing mandatory delivery contracts for
sale and purchase between the Lender and Fannie Mae.) This fee will be drafted
by Fannie Mae from the Lender's designated account immediately following the
Expiration Date of this Master Agreement. Fannie Mae's right to receive such a
<PAGE>
 
fee is in addition to any rights and remedies of Fannie Mae provided by law or
the applicable Program, and the receipt of such fee shall not affect or impair
any such rights and remedies.

All Mortgages shall conform to the requirements of the Mortgage Selling and
Servicing Contract between Fannie Mae and the Lender, the Fannie Mae Selling
Guide ("Selling Guide"), and the Fannie Mae Servicing Guide ("Servicing Guide"),
as applicable, as they may be amended from time to time, except as modified by
the variances contained in this Master Agreement and in the applicable Contracts
(defined below) entered into pursuant to this Master Agreement. (Any pool
purchase contract, in the case of MBS transactions, and cash commitment
contracts or voice recordings, in the case of cash transactions, are referred to
herein as a "Contract.")

Each Contract entered into under this Master Agreement constitutes: (i) an
agreement by the Lender to sell the Mortgages to, and service such Mortgages
for, Fannie Mae and (ii) an agreement by Fannie Mae to purchase the Mortgages
and, in the case of MBS transactions, to issue its Guaranteed Mortgage Pass-
Through Securities (the "Securities") backed by such Mortgages to the Lender or
its designee(s). By execution of this Master Agreement, the Lender and Fannie
Mae agree to the terms and conditions set forth herein and in any Contract
entered into simultaneously with this Master Agreement.

The Lender shall not disseminate or disclose in any manner any of the terms or
conditions of, or the form of, this Master Agreement to any person or entity
other than Lender's employees and agents who need to know the same in order to
perform their duties for the Lender, and who are legally obligated not to
further disseminate or disclose the same, unless the Lender is required by law
to do so and has given Fannie Mae prior written notice of such requirement and
of the information required to be disseminated or disclosed.

The Lender's right to sell, and Fannie Mae's obligation to purchase, Mortgages
under this Master Agreement may be terminated by Fannie Mae prior to the
Expiration Date of the Master Agreement if the Lender has breached the Mortgage
Selling and Servicing Contract it has entered into with Fannie Mae, or any of
the provisions of this Master Agreement, or any Contract entered into pursuant
to this Master Agreement. The Lender's responsibilities and liabilities under
this Master Agreement shall survive the expiration or earlier termination of the
Lender's right to sell, and Fannie Mae's obligation to purchase Mortgages under
this Master Agreement. This Master Agreement and any Contract entered into
pursuant to this Master Agreement may only be amended by the mutual agreement of
Fannie Mae and the Lender. Each amendment shall be in writing and shall consist
of a transmittal letter from Fannie Mae to the Lender generally describing the
amended provisions of the Master Agreement or the Contract, together with the
newly revised pages of the Master Agreement or the Contract. The revised pages
of the Master Agreement or the Contract should be added to the Master Agreement
as described in the transmittal letter. The Lender shall acknowledge its
acceptance of the amended terms and conditions by returning to Fannie Mae a duly
executed copy of the transmittal letter.

The Lender may not assign this Master Agreement or any rights or obligations
hereunder. The Lender may not assign any Contract entered into pursuant to this
Master Agreement or any rights or obligations thereunder.

The Lender hereby confirms, by checking the appropriate section below, that:

                                                                         5/01/96

                           Master       No. MD01546
                                    MA - 2
<PAGE>
 
 X   It is not a federally-insured institution or an affiliate or subsidiary of
----       ----                                                                
a federally-insured institution.

____ It is a federally-insured institution or an affiliate or subsidiary of a
federally-insured institution, and

(a) the sale to, and (if applicable) servicing for, Fannie Mae of the Mortgages
delivered to Fannie Mae pursuant to this Master Agreement has either been (i)
specifically approved by the board of directors of the Lender and such approval
is reflected in the minutes of the meetings of such board of directors, or (ii)
approved by an officer of the Lender who was duly authorized by the board of
directors to enter into such types of transactions and such authorization is
reflected in the minutes of the board of directors' meetings; and

(b) this Master Agreement and any Contracts or amendments pursuant hereto,
together with the applicable Fannie Mae Guides and the Mortgage Selling and
Servicing Contract between the Lender and Fannie Mae, constitute the "written
agreement" governing the Lender's sale to, and servicing for, Fannie Mae of the
Mortgages delivered pursuant to this Master Agreement, and the Lender (or any
successor thereto) shall continuously maintain all components of such "written
agreement" as an official record.

The Lender must accept this Master Agreement by returning a duly-executed
duplicate original to Fannie Mae within ten business days of the date of this
Master Agreement. If the executed Master Agreement is not received by Fannie Mae
within ten business days from the date hereof, Fannie Mae may at its option
declare this Master Agreement null and void.

Sincerely,

FEDERAL NATIONAL MORTGAGE ASSOCIATION


By:___________________________________________
     Jerome Brister
     Regional Vice President

Agreed, acknowledged, and accepted this 9th day of May, 1996.
                                        ---                   
HOME, INC.

By:___________________________________________

Name:  John W. Ballard
     -----------------------------------------

Title:  President/CEO
      ----------------------------------------


                                                                         5/01/96

                           Master       No. MD01546
                                    MA - 3
<PAGE>
 
                                   EXHIBIT 1

<TABLE>
<S>                           <C> 
Master Agreement Number:      MD01546                                        
                                                                             
Effective Date:               MAY 1, 1996                                    
                                                                             
Expiration Date:              APRIL 30, 1997                                 
                                                                             
Parties to Agreement:         HOME, INC. AND THE FEDERAL NATIONAL MORTGAGE   
                              ASSOCIATION                                    
                                                                             
Lender Number:                23772-000-8                                    
                                                                             
Agreed Amount:                $12,000,000.00, PLUS OR MINUS 5.00% (MANDATORY)
                              $-0- (OPTIONAL)                                
                                                                             
Back-end Buyout Fee:          The greater of $1,000.00 OR 12.50 BASIS POINTS
                              (.1250%) multiplied by the undelivered and
                              uncommitted portion of the Mandatory Agreed
                              Amount.
</TABLE> 

                                                                         5/01/96

                           Master       No. MD01546
                                    MA - 4