My daughters boyfriend lives in a motel room with his 5 year old and she wants to move in?

My daughter recently turned 18 and she met this guy a year ago she began dating. Hes now 20 and has a 5 year old daughter that he raises alone (the child's mother died in a car accident two years ago). Ill call him Will. Will moved out of his parents house two months ago after a fight with his dad, and he moved into a motel room on the third level of a locally owned motel which he pays $500 a month for. I went over twice for various reasons and the motel is not very nice at all. I hear things about it and hes barely making it. I now learn my daughter wants to move in to cut costs as soon as shes 18. I am totally opposed to my daughter, at 18, living in a cheap motel with her boyfriend of 20, who works as a part time manager of a fast food restaurant and a 5 year old child. I learned once social services got called and they decided since he was raising the girl, clothing her, feeding her and giving her fatherly love nothing was wrong and they said the situation was fine. I hate the thought of my daughter being there in that mess. The motel room is barely big enough for two beds and that means my daughter will have to sleep with her boyfriend right next to the bed that the 5 year old will sleep in and what kind of an example is that? Does anyone see my reasoning? How do I deter my daughter from this? And does anyone object to Will's living arrangements?