Does your son have any mental or physical disabilities? If not then he needs to find a way to pay his own bills. It would be a little different if he was working and going to school but if he is just working then he needs to find a way to pay his own bills.

We are kinda having the same problem with our daughter. The difference is she is 19 going to school and working part time but wants us to pay for everything while she lives with her boyfriend. My husband put his foot down tonight it was not pleasant but she was to act grown up without all the responsibilities.

If your son does approach you about moving in with you set rules in writing and what he has to pay you