Hi Steve,
Don't even lose sleep over it. I'll Paypal you $250 in three payments, and buy it from you.
J
I'd not offer a "Payment plan" It'll stress you out when he makes one, skips one etc. THEN he'll have a leg to stand on when you try to back out of the deal, with the argument that he''s making an attempt. Stop the bleeding. Be nice about it, give him the opportunity to back out (protect your reputation, etc. ) but stop the bleeding.
Bright side, he DID however give you an opportunity to add your experience in building, and customer relations. Thank him for that. Then challenge him on raising the bar on integrity, or whatever the issues were. Leave with your head held high, integrity intact, peace in your soul. And remember,
Father knows best.