Under WA law can I be held responsible for being a co-signer on a loan?

Whenever you sign as a borrower or a co-signer on loan documents, you become responsible for the repayment of the loan.

Generally, the loan document has a clause that allows the creditor the choice to go after any of borrowers and co-signers. Depending on the circumstances, you may end up being the only one the bank can find, the easiest one for the bank to sue, or the one with the most means of repaying.

You wrote that there is equity 5 times the amount of the loan. Do you know whether there are more senior liens against the property? What if the property burn down while its insurance coverage lapsed?

You may want to review your facts and options with an attorney.