The first step is the details. Scroll down to the bottom of this section to define the purchase price, offer date, expiration date, and closing date.This is a basic tutorial on writing up an offer for a WA single family home only. A Washington residential purchase agreement is used when making an offer to purchase real estate. The agreement initiates the negotiation process. Learn how to write a house offer letter that will be sure to make you stand out from the competition. Utilize a Letter of Intent (LOI) to initiate negotiations for a sale, summarizing the terms of a forthcoming contract agreement. Understand key disclosure requirements for sellers in Washington state and learn how to comply effectively. Here are 9 tips to draw a For Sale By Owner contract in Washington: 1. Write a Clear Title 2.