Perhaps you should talk to your son about what his plans are, what you can do to help, and what you’re willing to do to support him. Talk about what you’re okay with–he can stay with you at home as long as he’s actively job searching, he can stay with you for X amount of time and then he has to pay rent or move out, etc. If he knows he has a deadline (and perhaps, you’re not willing to have him come home at all, in which case his deadline is graduation), then it might kick him in gear to figure something out more quickly. He’ll figure out something when he realizes his parents and/or friends won’t support him financially forever.
Is he job searching? Is he thinking about graduate school? Has he talked to anyone at the career center? Did he do any internships or does he have any work experience? What is his major? Remind him that his first job doesn’t necessarily have to be his entire career path, but it’s okay to just have something that pays the bills while he is figuring it out.