Mom of 21-year-old RAS (IV heroin). Get him help now. Whatever you can afford/insurance will cover. As previous poster pointed out, whatever he learns in rehab or any type of structured program will not go to waste.
Take the car away. Illness is inconvenient and expensive. Get to meetings--Naranon, Alanon, Families Anonymous--whatever is available. It's free and it's effective.
Praying God grants you a clear head and a calm heart.