Please also review the separate Contra Costa County or city specific Ordinances and Regulations for property in the area you are either selling or buying. This Addendum is intended for use in the unincorporated portions of Contra Costa County.The document is an agreement for sale between Ms. Sowmya Lakshmi (Vendor) and Mr. A.C. Hari Prasad (Purchaser). This form is intended for use with the. 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. Official Forms for Viewing and Downloading. This Addendum is intended for use in the City of San Pablo. Please also review the separate Contra.