This form is intended for use with the. Official Forms for Viewing and Downloading.A California purchase agreement contains all the provisions, disclosures, and general information needed to secure a binding contract. This Addendum is intended for use in the unincorporated portions of Contra Costa County. A purchase and sale agreement is a contract between a buyer and seller for transacting a property in exchange for a specific price. Your agreement needs to say that you both agree to end the marriage and what you agreed about property or spousal support.