Fortunately, he doesn't have any student loans to pay down. That would have been my #1 piece of advice, if he did.
While, technically, buying a car or a bunch of stuff wouldn't really change his static assets (other than by depreciation), it would according to the FAFSA. The FAFSA wants to know about your money with a paper trail - bank accounts, investments, real estate, etc. It's not counting for the value of your TV, car, clothing, etc. On the same note, yes, it is still technically an asset if it is under the bed, but it's not an asset the FAFSA is looking for to determine your student aid package. Plus, family could steal the money, which is the major concern with Suitcase Full Of Cash scenario. Likewise, BIL is interested in buying a house once he has more credit and a higher income, and wants to save the money for that - or other important milestones, like his graduate degree. Keeping it liquid will give him an advantage after graduation.
Final scenario is a family member who is fiscally responsible (probably us) could hold the money for him for a year. Kind of reluctant to do this if there's a more independent way he could do it by himself.