No, you do not need to pay his rent or his health insurance, he needs to do that, he does that by seeking a program, getting sober and getting a job.
He has you wrapped around his little finger, what will happen if you die? What will he do then? You have not allowed him to grow up, and you are fighting this progression, the progression of life he is entitled to, that to become a responsible adult, to fly on his own.
I know you love him, love him enough to let go and allow him to forge his own way.
Turn his life over to him, it is his right of passage.