lostsoul25,
Do whatever makes you comfortable.
When my sons lived at home, especially the oldest, he had to move because of his extending my boundaries, and being argumentative. Was it because he was using? Didn't matter much to me, you live here, you're drug free, and someone I WANT to live with.
IMO, it makes no sense to ask if they're using, they get all arky-barky, and deny it anyway.
Hugs....