Learn how to fill out the Washington state vacant land purchase and sale agreement in our step-by-step guide! Customize the agreement: Fill in the template with specific details of the transaction.Washington Land Contract Template. A Washington land contract is a formal sale agreement between two parties transferring ownership of vacant real estate. Edit, sign, and share washington state vacant land purchase and sale agreement form 25 online. To fill out this agreement, first provide the date and the names of the Seller and Buyer.