I don't smoke, but need help with a friend who has developed a serious problem.

A friend of mine is literally high 24/7. Never leaves the house. He has lost his scholarship and is on the verge of becoming homeless, I have covered his rent for the last month (he lives with me atm) after his girlfriend cheated on him (3 months ago) he took it hard, so I did the friend thing and helped him out. He pretty much went from never smoking to smoking his entire paycheck each week(He started smoking shortly after his girlfriend and him broke up). He lost his job today and I am pretty sure he has begun doing illegal things (not sure what) to get weed.

He is a grown up and can do what he likes but I can't sit by watching him destroy his life. I have no idea what to do, i don't want to just kick him out because I think that would seal the deal with him ruining his life, I earn enough to support him in the bills/food/rent area if I am forced to while he cleans up his act/looks for a job so the 'time' factor isn't a problem. Whilst I know weed isn't "addictive" in the same way as other drugs, i know people can get addicted to the feeling, and I am just looking for more information on how I can help him get it under control.

Note: I worry this will be taken as a "Drugs are bad mkay" post, just making it clear I believe weed should be legalized ect. But my friend really needs to sober up.