just a logical opinion, but if the guy knows that the cab doesn't work cause of a blown fuse, then why wouldn't he spend the 2 dollars max it would cost to buy a new fuse and replace it? then the cab would "work" like he says and he could sell it for more. i think the guy isn't telling the truth, at least about the blown fuse. and like others have said, fuses don't blow, then fix themselves, then blow the next time. it's a bigger problem.
that aside, if it's 50 dollars he wants for the stuff, you could probably make your money back from selling stuff, worse case scenario. if he wants 100 or more, it's all up to you.