Unfortunately the buyer has to be the final QC inspector. Go through the unit with a fine tooth comb and maybe take a buddy that knows something about trailers with you. Do this before you sign anything or turn over any money. I have a Jayco 28RLS. My wife and I checked ever system, opened every door, flipped every switch, checked every outlet, etc., etc. spending three hours doing it. Fortunately we found no issues and have gone through a full season without experiencing any issues. Take your time and do it right the first time.