Bill of Sale and Assignment. A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price.This business sale agreement template can be used as a binding document to govern the sale of a business to a new owner. A sales agreement is used to describe and track the exact details of quantity and cost of purchasing or selling goods, services, or real estate. A Sales and Purchase Agreement (SPA) is a legal contract that details the agreement's terms and conditions. The letter of intent and the Asset Purchase Agreement should identify the assets and the purchase price.