Exhibit 2.4
 
                        SENTRY PARK WEST OFFICE CAMPUS
                            BLUE BELL, PENNSYLVANIA
                                        
                 THIRD AMENDMENT TO REAL ESTATE SALE AGREEMENT
                 ---------------------------------------------
                                        

     THIS THIRD AMENDMENT TO REAL ESTATE SALE AGREEMENT (the "Third Amendment")
is made as of the 30th day of May, 1996 by and between SENTRY WEST JOINT
VENTURE, an Illinois joint venture partnership ("Seller"), with an office at Two
North Riverside Plaza, Suite 600, Chicago, Illinois 60606, and BGK PROPERTIES,
INC., a Delaware corporation ("Purchaser"), with an office at 330 Garfield
Street, Santa Fe, New Mexico 87501.

                                   RECITALS
                                   --------

A.   Seller and Purchaser are parties to that certain Real Estate Sale Agreement
(the "Initial Contract") dated as of March 25, 1996, as amended by that certain
First Amendment to Real Estate Sale Agreement (the "First Amendment") dated as
of May 9, 1996 and that certain Second Amendment to Real Estate Sale Agreement
(the "Second Amendment") dated as of May 24, 1996 (the Initial Contract, the
First Amendment and the Second Amendment are collectively referred to as the
"Original Agreement") for the purchase and sale of the certain real estate and
improvements located thereon in the City of Blue Bell, County of Montgomery,
Commonwealth of Pennsylvania, as such real property is more particularly
described in Exhibit A attached to the Initial Contract.

B.   Seller and Purchaser desire to modify the Original Agreement as herein set
forth.

     THEREFORE, in consideration of the above recitals, the mutual covenants and
agreements herein set forth and the benefits to be derived therefrom and other
good and valuable consideration, the receipt and sufficiency of which are hereby
acknowledged, Purchaser and Seller agree as follows:

1.   DEFINED TERMS.  Each capitalized term used but not defined herein shall
have the meaning ascribed to it in the Original Agreement.

2.   WAIVER OF ENGINEERING AND ENVIRONMENTAL PERIODS.  Effective as of the date
of this Third Amendment, Purchaser hereby waives the conditions precedent to
Closing set forth in Sections 8(C) and 8(D) of the Original Agreement.

3.   CREDIT AGAINST THE PURCHASE PRICE.  As a result of Purchaser's review of
the Property and other matters pursuant to and in accordance with the provisions
of Section 8 of the Original Agreement, Purchaser has requested that Seller
provide, and Seller hereby agrees to provide, a credit at Closing against the
Purchase Price in the amount of Three Hundred Thousand Dollars ($300,000.00)
(the "Due Diligence Credit"). Purchaser hereby acknowledges and agrees that the
Due Diligence Credit constitutes full, sufficient, complete and adequate
consideration for Purchaser's agreement to purchase the Property in its "as is"
condition, as more particularly provided in the Original Agreement.

 
4.   BROKERAGE.  Section 6 of the Original Agreement is hereby deleted and the
following is hereby substituted:

     "Seller has agreed, pursuant to a separate written agreement with Penn
     Square Properties, Inc. ("Penn Square"), to pay upon Closing (but not
     otherwise) a brokerage commission to Penn Square for services rendered in
     connection with the sale and purchase of the Property. Seller shall
     indemnify and hold Purchaser harmless from and against any and all claims
     of Penn Square related to Seller's agreement to pay Penn Square a
     commission in connection with the purchase and sale of the Property,
     including, without limitation, reasonable attorneys' fees and expenses
     incurred by Purchaser in connection with such claim. Seller hereby agrees
     to pay upon Closing (but not otherwise) a brokerage commission in the
     amount of Fifty Thousand Dollars ($50,000.00) (the "BGK Commission") to
     Purchaser's affiliate, BGK Realty, Inc., a Delaware corporation ("BGK
     Realty") in connection with the sale and purchase of the Property. In the
     event that Seller receives a written notice executed by both BGK Realty and
     Purchaser prior to or at Closing requesting that Seller pay the BGK
     Commission to another affiliate of Purchaser ("Purchaser's Affiliated
     Broker"), Seller shall pay upon Closing (but not otherwise) the BGK
     Commission to Purchaser's Affiliated Broker. Purchaser shall indemnify and
     hold Seller harmless from and against any and all claims of BGK Realty
     and/or Purchaser's Affiliated Broker: (i) for a commission in excess of the
     amount of the BGK Commission, (ii) for payment of the BGK Commission in the
     event that the BGK Commission is paid at Closing by Seller to BGK Realty or
     Purchaser's Affiliated Broker, and (iii) for a commission in the event that
     the Closing does not occur, including reasonable attorneys' fees and
     expenses incurred by Seller in connection with such claims. Purchaser's
     indemnification obligation set forth in the preceding sentence shall
     include indemnification from and against any and all claims of all brokers,
     finders or other entities or individuals claiming by, through or under BGK
     Realty or Purchaser's Affiliated Broker, and reasonable attorneys' fees and
     expenses incurred by Seller in connection with any such claims. Seller and
     Purchaser shall each indemnify and hold the other harmless from and against
     any and all claims of all brokers and finders (other than: (1) a claim by
     Penn Square against Seller of the type described above, which claim Seller
     shall be obligated to indemnify Purchaser against as provided above, and
     (2) claims by BGK Realty, Purchaser's Affiliated Broker or any and all
     other brokers, finders or other entities or individuals of the type
     described above, which claims Purchaser shall be obligated to indemnify
     Seller against as provided above) claiming by, through or under the
     indemnifying party and in any way related to the sale and purchase of the
     Property, this Agreement or otherwise, including, without limitation,
     reasonable attorneys' fees and expenses incurred by the indemnified party
     in connection with such claims. The provisions of this Section 6 shall
     survive the Closing or other termination of this Agreement."


5.   RATIFICATION.  It is expressly understood and agreed that the Original
Agreement, as hereby amended, shall continue in full force and effect in
accordance with its terms and all references in the Original Agreement to the
term "Agreement" shall mean the Original Agreement as modified by this Third
Amendment.

6.   SECTION HEADINGS.  The section headings used herein are for reference
purposes only and do not control or affect the meaning or interpretation of any
term or provision hereof.

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7.   GOVERNING LAW.  This Third Amendment shall be governed by and construed in
accordance with the laws of the Commonwealth of Pennsylvania.

8.   COUNTERPARTS.  This Third Amendment may be executed in two or more
counterparts, each of which shall be deemed to be an original and all of which
taken together shall constitute one and the same instrument.

9.   CONFLICT.  In the event of a conflict between the terms and provisions of
the Original Agreement and the terms and provisions of this Third Amendment, the
terms and provisions of this Third Amendment shall control.


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     IN WITNESS WHEREOF, Seller and Purchaser have executed and delivered this
Third Amendment as of the date first above written.

                    SELLER:

                    SENTRY WEST JOINT VENTURE, an Illinois joint venture
                    partnership

                    By:  Blue Bell Associates, an Illinois joint venture, as
                         managing general partner

                         By:  First Capital Income Properties, Ltd. - Series XI,
                              an Illinois limited partnership, a general partner
                              of Blue Bell Associates

                              By:  First Capital Financial Corporation, a
                                   Florida corporation, as the general partner
                                   of First Capital Income Properties, Ltd. -
                                   Series XI

                                   By:  /s/ Douglas Crocker II
                                        ---------------------------------------
                                   Name: Douglas Crocker II
                                        ---------------------------------------
                                   Its: President
                                        ---------------------------------------

                         By:  First Capital Income and Growth Fund - Series XII,
                              an Illinois limited partnership, a general partner
                              of Blue Bell Associates

                              By:  First Capital Financial Corporation, a
                                   Florida corporation, as the general partner
                                   of First Capital Income and Growth Fund -
                                   Series XII

                                   By:  /s/ Douglas Crocker II
                                        ---------------------------------------
                                   Name: Douglas Crocker II
                                        ---------------------------------------
                                   Its: President
                                        ---------------------------------------

                    PURCHASER:

                    BGK PROPERTIES, INC., a Delaware corporation

                    By: /s/ Edward M. Gilbert
                       --------------------------------------------------------
                    Name: Edward M. Gilbert
                         ------------------------------------------------------
                    Its: President
                        -------------------------------------------------------

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