Personally I'd pass. It is a 98 model
1998 Trek 930 - BikePedia
The fork by this time is probably junk and even if it still works it is still a crappy elastomer shock with only 2.5" of travel.
Robot Check
The wheels are nothing special and weigh a crap ton. The tires don't look very good for mountain biking. The drivetrain from the pics looks factory stock to me so maybe he replaced the chain and cassette.

It isn't bad bike but I wouldn't pay $180 for it. Get on facebook and look for some local bike groups. Ask if any of them have an older entry level bike laying around they would sell.

also did you mean 16.5" for the size? That would probably be perfect.