A Washington residential purchase agreement is used when making an offer to purchase real estate. The agreement initiates the negotiation process.A Washington purchase agreement documents the sale of a piece of real property for a specified financial figure. Ensure you know the legal requirements and disclosures of a Washington real estate purchase agreement. Fill in our template to create your agreement. The completed document will describe the property being sold, purchase price, closing date, and closing costs. Seller agrees to sell to Buyer and Buyer agrees to purchase from Seller the following described real estate in __________________ County, State of Washington.