The residential purchase agreement can be used to negotiate compensation from the seller to the buyer's broker. CAR (California Association of Realtors) residential purchase and sale agreements are widely used in real estate transactions throughout California.California Realtors (CAR), use a contract entitled Real Estate Purchase Agreement, including Escrow Instructions and Notice to Perform. The form can be used with a Commercial Purchase Agreement. (C. California law prohibits a dealership from giving a customer a purchase agreement before the vehicle is on their property.