If they still do things the same way in the USMC..
Get him a pre-paid Visa or MC.. put some money on it, and tell the family they can do the same (try to keep it to one card).
I talked to the Marine Recruiter a lot, and heard some horror stories about finances while in Basic.
This is my understanding, maybe somebody will post if I'm right or not: While in Basic Marines do not get paid, or they do, but their pay is withheld until after Basic.
Their first paychecks are pretty much taken to pay for their uniforms and other required necessities.. so even after Basic they don't have a big pile of money waiting for them. From what I understand (again) is the Marines are the only service that require their marines to pay for their own uniforms, and they're not cheap.