Mikey,
The people at the Residential Treatment Center (RTC) will not lose their homes if you get sued because you knowingly allowed a substance abuser to drive your car. If they think he needs a phone, let them pay for it.
We have all been there before. My difficult child comes across as a sweet young thing that would never do anything wrong. She has fooled many a therapist and counselor. She refused to keep going to the only one that saw through her act right away.
You have to do what you know is right. Your difficult child feels entitled to things because you have always provided them with no conditions. What has he ever done to earn these things? Why would he value them if he didn't do anything to earn them?
The last time we provided our difficult child with a phone was when she was 16 and I found a local drug dealer on her speed dial. I told her that I was not financing her connections to her druggie friends. After that, she either didn't have a phone or she paid for it herself. I found that you don't need credit for Metro PCS since you have to pay in advance every month. It also has unlimited local calls for about $45 a month so my difficult child can't screw it up. It was the perfect answer for my difficult child. She still uses them.
I would check on that sort of thing for your difficult child and if it is available tell him that he is old enough now to pay for his own phone. You can deactivate his line on your plan without getting hit with cancellation fees.
Show him that you mean business. He will not be motivated to change unless his situation changes.
by the way, does he have a job?
~Kathy