A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price. BUYER agrees to purchase and SELLER agrees to sell the real property, and the improvements thereon, commonly known as: , in the County of.A California purchase agreement contains all the provisions, disclosures, and general information needed to secure a binding contract. 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.