If you found out your 29 year old homeless son had been on Meth what can I do?

I found out from a friend of my son that my 29 year old homeless son used to be on Meth. My son has no job and is sleeping in his van for the past 7 months. My son says he is not on drugs. That he just has bad luck. His friend used to do it with him but got help and went through rehab and found GOD. What can I do to help my son? Please help!