Legal Question in Personal Injury in Washington

This sounds like a recipe for disaster to me. Why not have the agent who is picking up the RV simply show up with a cashier's check for the $39,500 purchase price, and you sign the title over right then and there? If it is a matter of the buyer needing to save up for the 4 payments, take a non-refundable deposit, giving him a predefined period of time to come up with the balance, and if he does so, great, otherwise, you keep the deposit and are free to sell it to someone else.

Worst of all, what happens if during the period between these payments starting and the agent showing up to take title, the motorhome is damaged and there are problems with insurance, etc.? What if the buyer claims the motorhome is not as advertised, or has some other reason to try and back out of the deal?

I would just do all I could if I were you to make this as simple a transaction as possible. Have one payment. Transfer title upon this one payment. If the buyer can afford to pay you in four payments of ~$10,000, then he can get a loan so you can get paid, and he can pay the bank off in four $10,000 payments. It should not be your problem. If he needs time to come up with the money, then take a non-refundable deposit, so that you can keep it off the market during that time. I recommend 10% in this case. That puts pressure on him to follow through as well. Whatever you do, make sure you have a well written contract that specifies all of this, especially if you take a deposit.