Hi Eve13 I feel your pain. My personal experience is that it is hard to live with adult children even if they don't have an addiction. It gets complicated. At one point, I had two adult sons, a teenage daughter, and my mother in the house with us. We like to have order in the house and when you have adult children they want to come and go as they please; it gets a little irritating. One day, my husband and I were discussing that sons were too comfortable. And I thought, I do not want them living here and be like that movie "Stepbrothers" being 40 and still living under our roof. So I told my eldest son, who was 21 years old at the time, you have to start looking for a place. I would go out every weekend to look for apartments with him (AS was in county jail at the time and would end up being there for about 11 months). At the time, we were fortunate to be in a good position financially, and my husband decided we should just buy a condo near the university that the boys could rent from us. We figured that being right across from university might inspire them to some day go back. We told them that they would get a better deal on the rent that just a stranger off the street. We did tell them that once they are out of the house they couldn't come back. So now, this is the only home they have. If they mess it up, they are out of luck (being that there is an HOA for the condo, I made it very clear that if I got enough complaints, I would have to evict them because the HOA would hold me accountable and I didn't want to deal with that if they wanted to live there). My eldest son lived at the condo for about three years and recently moved out to go live in another state. My AS is recently living there with my youngest daughter who is in her second year of college. They both don't pay rent at the time but I am letting the get situated and they both know they won't be allowed to move back home under any circumstance for my sanity and my husband's sanity. The only kid I have at home is my mother. LOL. It is much better this way. At least with the independence, they are more accountable for themselves. My AS likes to keep the condo clean and is respectful of his sister because he knows that he better not put her in any danger or hurtful situation. We made it very clear that he needs to look out for her and be there for her not put her in harms way, otherwise I would have no choice but to ask him to leave.
I know not everyone has the ability to just go out and buy a place, but to us it was worth having some peace of mind and also helping our children learn how to be more independent. They have to rely on themselves for day to day stuff, i.e. cooking, cleaning, laundry, some bills, abiding by HOA rules, etc. I'm not in there telling them what to do all day, and we probably save a whole lot more money than them coming in and out or saving them from whatever situations they could get into financially. We did tell them, though, that if they ever leave the condo, they are not allowed to come back there (my oldest is out). Once they are all out of condo, we will rent it or sell it when we retire (kind of an investment for us).
Not sure if this helps. The moral of the story is that if there is an opportunity for them to be out from under your roof, life is at least a little more peaceful.
Good luck.