The 2000 and up year models are pretty darn bulletproof. POGs were replaces with steel starting in 2000, so that won't be an issue. Once it has over 30-40k miles, it may need cam chain tensioner extenders, but that's an easy fix.
Other than that, the most common problem is the owners who get on them and start riding frequently don't want to come back!
Other than that, the most common problem is the owners who get on them and start riding frequently don't want to come back!