I assume you are talking about more than the $5.5K federal student loan. He is likely not going to be able to take out a private loan without a co-signer…does he have that person lined up for the next four years? Have you researched other options like parent plus loans, home equity loans, etc?
Here is a loan payment calculator so that he can model what his payments will ultimately be. Mapping Your Future: Student loan repayment calculator