I would look closely at a few things.
By far the weirdest is the fresh water tank which was a plastic bladder that lives under the rear dinette floor.
I have never even seen one as mine had already been removed before me but I am told that when filled up,the floor will rise from it it !?!
I would want to know going in if I were going to be dealing with that or if a newer tank was already in place somewhere else.
I would also look under the seat areas in the sorage space and see if the wood is rotted or not.
If water leaked into there and sat on top of the fiberglass there is a chance it also rotted out some plywood.
I would also look at the frame where it exits the trailer at the front for signs of rust-thru or cracking which were the cause of a recall by Trillium
Welded gusset plates would be an indication that this was already fixed.
Otherwise almost any part of these can be restored/repaired fairly simply.
Take the checklist with you and have fun.