I've bought many RV's from salvage auctions. ...and autos, hundreds and hundreds of autos.
Never had a problem.
But understand that it is totally "as-is".
Most auctions will have a day you can go in and inspect the units before the sale date.
I don't buy fiberglass campers. Much to hard to repair.
Aluminum siding campers are a piece of cake to repair.
Floors are the most difficult repair, anything above the floor is not that difficult.
Also, don't try to re-invent the wheel.
Make repairs in the same manner as originally built.
I get most of my supplies from All-Rite.