Just because it had some water damage doesn't mean it is still leaking, it also doesn't mean it won't leak again or in another spot. I have a camper that I bought with a leak. I thought I did my due diligence and checked it thoroughly, with a moisture meter. (they don't work very good on RV walls). I found the leak on a rainy camp trip the first fall I owned it. It took a repair shop multiple tries and a couple grand to stop the leak and repair anything that got we, although not very wet and never had mold or rot. I would say now, a couple years later, that it does not leak and there is very little if any evidence that it did leak. There are a couple places on the exterior wall where I believe there is some delamination, but that was due to the repair process. As they pulled things apart, I didn't want to pay to have the entire wall removed, so they did what they could.
Mine is a 2007, which I have had for a about 4 years now. The price was very good, so even with the repair cost, I got a good price on the unit. If it is repaired correctly, and not leaking, then there is no reason to think it will leak again any more than any other spot on the horrible construction of an RV.
But, like someone else said, do what I did not do, and hire an RV Inspector to look more thoroughly than the average person could. OR, take it to a place that does RV repairs and have them go through it. The couple hundred bucks you pay now could save you a lot later. If the person selling won't let you do those things, then don't buy it and move on.
