It's your house so the golden rule applies here. You have the gold, you make the rules. As a father myself I would allow my daughter and her boyfriend to move in under normal circumstances, but if he's on oxy that's not normal. You have enough on your plate w/o having to deal with a practicing addict under your roof. You have to be selfish here, dubs, because your own recovery has to take presidence over all else. And I would explain the situation in that manner, as well as reiterating any moral issues you have.