I'm with Francesca, the seller backing out may be good news for you. Perhaps he was told that it wasn't safe for the tow or feared that you would back out when you saw the condition.....
As I have oft mentioned, we drove 350 miles one day to buy a
SCAMP only to have the seller sell it our from under us when we were 10 minutes from his house.
One of my basic rules in buying: Good ones don't last long, they usually sell within a few days or are either overpriced or Junque. I think that one was
for sale for about a month before you got in line for it.
And BTW: Always buy the very best you can afford, fixers are very expensive if you can't do all your own work.
Walk away and be happy, and ferget any deals he offers.....
Good Luck and look here: at least twice a day:
Molded Fiberglass Trailers | Fiberglass RV's For Sale