I understand your situation. I think your situation is what my mother would have preferred, but having tried to assist when my father was ill- and experiencing what you have- not able to sleep, being worn down emotionally and physically with her constant demands, I knew I couldn't do that.
I had wanted to be of help, but in what I had seen as a "normal" arrangement between an elderly parent and adult child may have some challenges but also there was some mutual caring, trust, and cooperation between them.
None of this was present with my BPD mother. While her children are reliable, BPD mother was not. She hid information from us, lied, and had no concern for our well being. For her, it was about what she wanted. Yet, she could not manage on her own.
In BPD mother's state, the law protects the elderly person. If BPD mother was angry at a caretaker for having boundaries, she would call it "elder abuse". While she never pursued this legally- this scared them, and some refused to work with her. While I understand your plan and your feelings- one concern is if your mother accuses you. A parallel concern in relationships is if the man is being abused, and calls 911, sometimes the woman with BPD then accuses him. The law is biased when it comes to male and female abuse and sometimes calling 911 on the abusive wife results in her false claim of abuse and the man is arrested.
In the US, the system for elder care leans heavily on family. Most assisted living is self pay and not covered by Medicare/Medicaid. Since your mother has resources, these could be put towards that, which would require some discussion and agreement on her part. While this situation still can be challenging ( and it was still with BPD mother), it is less of a strain on you in terms of daily caregiving.
If family isn't available, or able, there may be a way for the state to take guardianship of that person.I didn't pursue that path, so I don't know the details. There was a poster here who did that. At first, he brought his BPD mother to his home, like you did but it was not a safe situation for his children, and so- she eventually became a ward of the state.
These kinds of laws are state specific. While your wish to not take on your mother to this extent is understandable- whether or not your ability to claim abuse holds in your mother's state- or puts you at risk - I don't know. Maybe you do already since you have a law background. I don't, so I asked.


