Get a inexpensive bike that is the right size for cheap. Go over it with a fine tooth comb and make sure it's properly put together. For a beater bike at college with short commutes, that's all that is needed.
If he will also be doing longer rides for fitness or enjoyment, then that's another story and another bike. So he can be N+1 at the start of his college. One bike to use for going to class and can be locked up outside. The other to keep in his dorm room and never take his eyes off of when out for long rides.