Parties: the "SELLER," agrees to sell and. , the "BUYER," agrees to buy, the premises described in paragraph 2 on the terms set forth below.Use this form to change or amend terms of the Purchase and Sale agreement after it has been signed. A Massachusetts purchase agreement is the standard legal form for selling or purchasing a home. It documents the transaction's stipulations. A quick walkthrough of Massachusetts Association of Realtors form 503 it is the standard residential purchase and sale agreement. Review the entire agreement thoroughly. A Massachusetts residential purchase agreement is a legal document that secures a real estate transaction between a buyer and a seller. It lays out the framework for a conveyance (a real estate transfer) in Massachusetts. How to fill out a basic Listing Agreement.