In Washington, a purchase and sale agreement becomes binding when:

The buyer's signature alone constitutes only an offer, not a binding contract, because the seller has not yet agreed to the terms — one signature represents only one side of a two-party agreement.

Earnest money deposit is a performance step that typically follows mutual acceptance; it demonstrates the buyer's good faith but has no legal power to create the binding contract itself.

The inspection contingency is a condition that may allow a buyer to exit the contract after it is already binding; completing an inspection occurs well after the contract has been formed at mutual acceptance.