so when i say, i don't have any money...it means, "to spend" ....
Have him get a part time job. If I've learned anything from going to college and graduate school it's that employers look at work ethic and experience more than they do grades. A job will make him appreciate what he earns and establish budgeting habits that will benefit him in life. Sorry but I know this doesn't answer your question but I hope it gives you something to think about.
I think your right on the money depending on how much gas he uses to come home.