A Washington Residential Purchase Agreement form outlines the terms of an offer to purchase real estate, including the buyer's proposal and requested purchase price. A purchase and sale agreement in Washington includes a description of the real estate, tax parcel number(s), and personal property.Today I wanted to take it back to the beginning and discuss the residential purchases sale agreement now here in Washington State. A Washington residential purchase and sale agreement outlines the property being sold, purchase price, closing date, and other terms. A real estate contract washington is, at its core, a legally binding agreement made between two or more parties in a Washington real estate deal. A Washington purchase agreement form outlines the sale of real property, including any contingencies or conditions. Description of The Property.