Chris, it would be worth asking for a few more interior photos, and if it looks good, go see the trailer. If all it needs is a paint job, its a good deal. A lot of people paint their own eggs, and a good paint job can look terrific (but is a lot of work.) There is a checklist on this website for what to look for as far as condition of the trailer.
Look for Buyer's Check List about halfway down the page.
Since it is a pop-top, look at that specifically- what condition is the plastic, how is the mechanism working?
It sounds as if this guy is having trouble selling, which either means the paint job turns people off or the trailer has other problems. If you are willing to paint, and nothing else is wrong that would cost a lot to fix, might be a nice trailer.