Purchase and Sale Agreement. A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price.This written contract delineates the terms and conditions of a sale, encompassing various aspects such as goods, services, pricing, and transaction particulars. How do I fill out the Purchase Contract? Enter property details, purchase price, and terms in the designated fields, and review the document before signing. A Sales and Purchase Agreement (SPA) is a legal contract that details the agreement's terms and conditions.