Agree -- Roth IRA is the way to go if he has earned income. I believe those are non-reportable for financial aid purposes.
If you can't do an IRA, then your next best choice is probably a custodial account.
Vanguard has some funds (Target Retirement and Star) that have the $1000 minimum, but the rest have $3000/$10,000 minimums. Vanguard does not cut custodial accounts any slack on the minimums -- it's still $1k/$3k/$10k. Schwab does -- you can do a custodial account there and get into any of their index funds with $100. Their index funds also have nice low fees -- many in the .03 - .04% range. Not sure about Fidelity and their minor funds.