That actually sounds like a pretty good deal at $800. Make sure there is no separation/delamination at the seams
Inflate the opposite chambers and look for blown baffles. The uninflated chambers should stay uninflated
Its not self bailing? A floor can get pretty torn up. Look carefully at the condition of the floor. You can also fill this with water and look for it to leak out.
Soapy water and a spray bottle is a good way to search for porosity leaks. If you get tiny bubbles everywhere its probably gonna need to be repumped up during a trip
Hey, if you want me to take a dump in a box and mark it "guaranteed", I will. I got spare time.