Use this form to change or amend terms of the Purchase and Sale agreement after it has been signed. A quick overview of the Massachusetts Association of Realtors exclusive right to sell listing agreement.The MAR Standard Form Purchase and Sale Agreement is designed to protect the interests of both the buyer and the seller in a property transaction. I wanted to walk through the basics of putting together an offer for you today. Clause 2—Description: exactly what is being sold. If a square footage for the land is listed, please make sure it what you are expecting to buy. How to fill out a basic Listing Agreement. The sales agreement will also cover a description of the property. Often additional parcels of land are being sold with a house. Utilize a purchase and sale agreement when conducting transactions that involve the buying and selling of goods or real estate.