1. See if the instrument cluster is properly grounded. If not, the tach will be goofy.
2. See if the gas gauge works.
3. Ask if the stator and R/R has been replaced yet.
4. Check to see if the headers have been modified.
5. See if the tail light assembly is intact. This part will break; it's just a matter of time. If it's still good, then I'd take it off and save it; use a fender eliminator instead.
6. Make sure the gas tank doesn't leak.
7. Make sure all the fiberglass is in good condition; try cannot be replaced.
8. Make sure all the fasteners are tight, and there's no signs of wear.
9. I'd check the clutch cable; I had to replace mine early on...
10. See if he's still using the crappy stock mirrors; they only show you your shoulders.
11. Check clutch feel, particularly finding neutral when in first gear.
My major issues have been electrical; the motor itself has been without a single problem.
There may be other issues, but these are the ones that come to mind...