What if you address it now and offer to help him save his money. Eg. - "We know May is coming and we'd like to help you make sure you have a roof over your head. Would you like help with getting a job? Maybe your dad and I could help you go through the want ads?" or

"We're concerned about your financial situation. How about getting a job and turning your check over to us. We'll help you set up a budget and give you what you need to live. That way, we'll be sticking your money away for you so you have it when you need it." Maybe you could even give him an incentive like, "If you save x amount of dollars before May, we'll give you X amount of dollars to show you how much we appreciate your efforts." I know that sounds crazy, but if he ends up moving in, you'll be spending a heck of a lot of money on him, plus you'll have the frustration of having a poor, sad soul in your midst.

Just some thoughts on a positive approach.