How Can I Help My Son Get Off Drugs, Heroin Is His Drug of Choice, I Have Spent $1,000 Already ?

We live in a small town in PA and sent him to CA for Rehab, came back feeling and doing great for about 5 weeks then back on the stuff again. His mother will not let hem stay with her, so he lives with Dad ( me) and has a hard time doing anything responsible for a long period of time. He is wasting away. Ideas ? Help ?