A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price. (Complete if applicable).Curious about the paperwork for selling a house without a Realtor? This FSBO paperwork is needed as soon as you accept an offer, so it's useful to have a purchase agreement onhand that you can fill out quickly. A purchase agreement is a form used for making an offer on a home. It contains a set of conditions and contingencies that are presented to the seller of a home. A purchase agreement is a legal contract between a buyer and a seller.