Avions are well regarded. The add is well written and the pictures look good. The body looks straight and interior appointments seem to be there. That may or may not be a comfortable futon but could easily be replaced. If left in a sleeping position you would only have the dinette seating for sitting in or on. Is there enough room for your pet. I'm not sure what the item next to the stove is, (left under pantry)
Pictures hide a lot of imperfections that an eye can see.
Most people price slightly higher living some room for negotiation.
You can also ask a forum member to go take a look at it or find an inspector on the forum to go do an inspection.