I am also the mother of an addicted son and want to welcome you too.
"We" are not their only hope or option. "We" are not the solution and if we enable we become part of the problem.
He has choices and doesn't have to live in his car. He can choose instead to call the Salvation Army and go to a rehab that will cost him nothing.
If he chooses to continue on his path of addiction, it will only get worse over time...and the worst place for any mother to be is in a front row seat to the drama.
If other family members try to make you feel guilty, then they need to find help for themselves too. Love cannot save our addicted children, if it could not one of us would be here.
Take a read around, the sticky posts at the top of this forum have some helpful reading. Make yourself comfortable and know you are among friends who understand here.
Hugs from one mama's heart to another's.