Like others have said, take your time and thoroughly inspect and try everything. Earlier this week I went and picked up a TT for my son since he really doesn't know much about them and had to work anyway.
I did the PDI for him. I tried everything in the TT. Unfortunately when I tried the pull down shades one side of one came loose and on another the strings were so loose that it wouldn't stay up.
Also the exterior door holder was missing a part. They promptly fixed those items while I waited.
I doubt my son would've caught those things as he would've been overwhelmed by the 1st time buying process. BTDT.
Don't be afraid to ask them to run everything. It's easier to find out something doesn't work at the lot than at home or out camping.
Good luck in your search.