Need Tough Love Advice

Hello Everyone, I need some sound advice from others dealing with similar issues.

I have a son that is 17 (turns 18 in 2/12). He recently ran away so he is no longer in school. The family that was helping him out kicked him out becuase he was doing nothing to move forward and started drinking, smoking pot and treating their home like a flop house. So he is back at our house.