Welcome! I am in love with an addict. I have been a member here for about two months now and I can honestly say....this forum has saved me so many times now.
It sounds like you already understand a lot about addiction and I think it is wonderful that you already know if he is using, letting him stay at your house would be enabling. Good for you to see that.
Addiction is hard but you will find a lot of support here. Keep posting and let us all know how you are doing.
Hugs