Welcome to our forum. If you would jump over to Parent Emeritus and read the stories there, you will see that you are both not alone and how many other parents handle these failure to thrive adult children, some who sadly have their own kids. Some grandparents try to get custody of the grandchildren. Some call cops or a lawyer the get that ball rolling. They are innocent in this. Your daughter however is an adult. Whole other story in my eyes
I personally would not financially care for or pay rent for a 30 year old adult child because that just encourages lack of motivation and dependence. They have no reason to grow up. Is there a reason your daughter can't work to support herself? Is she ill? Disabled? Have a restrictive diagnosis?
If so, she can apply for SSI, housing, welfare, food stamps and medical assistance. If this is all she wants from her life, this is what the end will be anyway as none of us can live forever. Sounds like she makes bad choices and could also use therapy and perhaps a social worker to help her learn to do life. I have a high functioning autistic son who will be 23 soon and these services were great for him...He is really fast tracking now, lives all alone, has a job, is kind and caring and makes awesome choices. He is very happy and well adjusted, autism or not. Adult kids sometimes listen to others whereas they usually throw toddler tantrums if we tell them anything or set any boundaries, like no more money. The using us as the Bank of America is an issue for most with unmotivated adult children. Many stop the flow or restrict it.
I think it's not good if daughter ever lives with you. The grandchildren, yes, and if you want custody, go for it. No boyfriend of any sort would use my house. Period. Do not let anyone, including your daighter, have so much power over you that there is no more YOU left. You and your husband and peace in your sanctuary (your home) matter. She should not be ruling how you live or taking up all your thoughts. Therapy could help both of you with clarity issues.
Anyway I'd hop on over to Parent Emeritus. Plenty of experience and advice on that forum.
Hugs for your hurting heart!