What to look for in an enclosed trailer?

My brother had a 22 ft. trailer which he put a butcher shop into.  I mounted an engine hoist on one rear corner to hoist Bambi up for ease of butchering.  He gets cash and the customer gets packaged meat, the hide, spare parts and the mess.    Mike sold it a few years ago because it was too much trailer for some locations.  He asked me to help him locate a good 14 ft. trailer.

So, rust is bad.  I prefer two axles because losing one of only two tires is bad, losing one of four is safer.  Anything else?  The last trailer ws insulated, had AC and 110 wiring for the band saw etc.  Any other suggestions, ideas?

Edit:

Would an old RV trailer qualify, structurally?

I think an RV trailer that short may be single axle. No clue if RV units are built any better/worse than cargo ones. For a shorter length cargo trailer, make sure there is ample ceiling height to work, entry doors may be shorter too. I have both an enclosed car trailer, 20 x 8.5 and an enclosed cargo, 16 x 7. The doors on the cargo trailer are just tall enough to fit through without ducking, I'm 5'10". Unless you luck out finding a used one spec'd out with exactly what you need, bite the bullet and get new. I spent 6 months looking (10 years ago) for my car trailer to end up saving $1500 over new, it wasn't worth it.  Nice LED lighting is easy now a days to add to your list.