Yeah, that price range will be old and/or crap. A while ago a friend would looking and could find NC1s (so 2006-2008) in the 80k mile range for around $8,000, but that's in Texas markets. Most of the cars were in pretty bad shape. One was moderately modified, but actually in decent shape, and the mods were quality parts installed properly. The mods scared off other buyers, so it was a relatively good car for its price.
If you're looking at 6MTs, expect the transmission to be notchy. It is. This is normal. Particularly 2nd gear when cold. I really like the feel, but some don't. If it's a bit more notchy than your friend would like, a different transmission fluid can help. If it's significantly too notchy, look to the 5MT (which is much smoother). The notchiness isn't a sign of a problem with the transmission, though. If you don't already know this, both 5MT and 6MT in the NC1 rev quite high on the freeway. As I approach 80 mph, I approach 4,000 rpm in 6th gear. Again, it's normal, not a sign of issues.
If the 6MT feels odd, grinds, or is stubborn about going into 4th gear (specifically), this is probably a misalignment of the 3/4 shift fork (it can affect 3rd as well, but it typically shows up on 4th gear first). It's an easy alignment to do, but your friend may not want to deal with it.
Take a good look at the top. There are a few potential issues. There are straps on the inside of the top, in the rear, near the rear window. These can fray or otherwise be damaged. On the tan cloth top, wear points can appear on the outside top corners. These are just discoloration (it happened to mine), but they're unsightly.
The seat belts may not retract well. There are retainer clips on the seats, and these grab the belts a bit too strongly. If you just... take off the belt, it retracts slowly. If you help it go through the clip, it should still retract fine. That probably doesn't make much sense without seeing the seats, but when you see the car, it'll make sense.
I don't remember any other NC specific concerns off the top of my head, but my car's been well behaved (other than some early warranty issues), so there may be things I don't know about.