I was seriously looking at one a few years ago so some recollections may be a bit rusty. The two major problems that seemed to crop up were the leaking ports/hatches and the holding tank. The holding tank is aluminum and will corrode through if it hasn't by now. Many were being replaced by bladder tanks which may just make a bad problem worse if not properly installed. You definitely want to check that issue.
The port and hatch problem could just be local leaks but could also be a major problem if they haven't been dealt with and water gets into the core. Leaks into the core could be a major problem if things haven't been re-bedded at some point. The "Hunter Owners Website" was a great resource for me while I was researching the boat. I really liked the design and the build quality was good I just couldn't swing the finances at the time. Good luck!