To me, if an owner doesn't bother to clean his bike, he probably doesn't bother to maintain it either.
carb rebuild (2-3 hours) serious bath (2-3 hours) oil/brake fluid change and brake inspection ( an hour plus some money), new tires?
500.00 as is
700.00 if it starts
more if it runs well and is cleaned up a bit
just my pocket-book talking