I came super close to buying a 10' fiberglass shell this morning. The price was right, but it was in awful shape! I mean worse than gutted, because someone tried to glue foam all on the inside, but did a crappy job and the tried to remove it. It needed a complete new floor too. This would be a complete rebuild. Me and the wife have been talking it over, but we just don't know if we should tackle it or not. I think if I did try, I would keep it as simple as I could. I wouldn't try to put a bathroom, just a porta potty, table, bed.
I wouldn't try to do a kitchen at all. About the most maybe a small sink, porta potty. Just a place to wash your hands. I would also keep the wiring to a minimum, since I don't know enough to do anything different.
My biggest concern is patching the holes it has. It's not cracked or broken, but all the rivet places it has. Someone just used a calk gun to squirt blobs all over the out side. The belly band also needs attention.
I think for the inside, I would do the Titebond II and canvas and then paint it. That might seal the holes good enough and then maybe I could use bondo or something similar on the outside.
It just seems like a lot of work, but I think it would be fun.
I'm still on the fence.