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

The buyer signing alone doesn't create a binding agreement. A contract requires mutual acceptance from all parties, not just one. The seller could reject the buyer's terms or make counteroffers.

Earnest money deposit is evidence of the buyer's good faith but doesn't create the binding contract. It's typically required after mutual acceptance, not as the triggering event for contract formation.

Completion of inspections relates to contingencies within the contract, not the formation of the contract itself. The contract exists before inspections are complete.