There is nothing wrong with that entry level Trek, especially if you can get it used at a good price. The fork will be worthless at his weight. If it is in the budget I would swap for a rigid. If it is going to be trail ridden, get a front tire that is an honest 2.4" or 2.5" ( in 26" I like the Maxxis Holy Rollers around here), so it can be ridden at moderate pressure without pinch flatting.