FYI, you son should also be aware that a bass player will have the following responsibilities once he starts playing in a band:
1. Must have a rehearsal space.
2. Must own reliable transportation, preferably a large truck or van, so he can drive the rest of the band to practice/gigs.
3. Must provide band P/A system, even (especially) if he doesn't sing.
4. Must have intimate knowledge of electronics so he can fix amps, pickups, pedals, P/A systems, etc, while at gigs or practice.
5. Must carry on him at all times: extra guitar strings, drum key, cords, 9 volt batteries, shoulder straps, etc.
That about covers it.
-as far as your original question, what others have said about used Fenders is spot on. You might even be able to find a decent new beginners "combo pack" at Guitar Center for a couple of hundred bucks. This will include a bass, amp, strap, cord, and maybe even a tuner. Not the best stuff out there, but fine for learning.
Jim