Here's what I'd suggest.... you can help him to get an easy to care for plant that he can cultivate as a pre-bonsai. The plant can grow with him through college and (if it survives) will be 4-5 years in development by the time he graduates. The cool part is that the plant will be developing at the same time he is. I know quite a few people who have that kind of sentimental relationships with their plants.
Many plants available at big box hardware stores can be a great fit for this, but it's CRITICALLY important that it's a plant that he likes because he's going to be looking at it thousands of times. It's a labor of love, so you have to make sure that the love is there. Otherwise, it's easy for the plant to be left behind in the shuffle.
There are some good houseplants that make eligible bonsai. Jades, Portulacaria, Schefflera, and Ficus all do double duty as houseplants and bonsai. You can grow them for 10 years as a house plant and then start the 3-5 year plan to convert into a bonsai when you like.
Other options that have a "flair of bonsai" are pachypodium varieties. They're incredibly unique and so easy to take care of.