Common forms and documents you will use in transactions. This is paperwork to use with a Purchase and Sale Agreement.A Washington residential purchase agreement is used when making an offer to purchase real estate. The agreement initiates the negotiation process. Learn the fundamentals of drafting an offer on a residential property in Washington State. Here are 9 tips to draw a For Sale By Owner contract in Washington: 1. Write a Clear Title 2. How to write an offer to buy a house that is listing on NWMLS. In this article, we will cover what you need to know about how seller financing in Seattle area works. A cash offer on a home is pretty straightforward: You find a property you want and then submit an offer to purchase it outright, without a mortgage loan.