Who is legally responsible for a dementia patient's healthcare? Is it the family or the caregivers?

I forgot to inform you that he gave his daughter power of attorney for his bank accounts a long time ago because she said she'd handle his finances for me but she hasn't done anything about it and won't call me or answer my emails. That's why I'm worried that she may do nothing to care for him after I give my notice.

Babalou, please forgive my ignorance, but what does APS mean? Adult Protective Services? I've already contacted them and they told me to call the Dept. of Aging for advice. If his daughter doesn't hire an agency to take care of him after my notice has expired then I go to Adult Protective Services, right?
Thank you so much for helping me.

Yes, you should notify his daughter, as the doctor suggests. But the daughter is not legally obligated to care for her father, in most states.

Does he recognize that he needs more help? ( probably not). You should notify APS that he is a person in need of care asap

I'm a friend who has been taking care of him for 3 years. He has been paying me about $500. a month. Now his dementia is rapidly escalating and I am no longer going to accept money from him because I feel he may not realize what he's doing, although he says he does. There is no contract and I am not a licensed caregiver. There was no one else so the job was dropped in my lap. I'm 68 and exhausted and scared. His doctor said I should write a certified letter to his daughter 2000 miles away and tell her I no longer am able to take care of him and that I should get away from all this stress and responsibility. If she doesn't respond, what do I do then? Thank you for any answers.

Are you "officially", (getting paid, with a legally binding caregiving contract in place?) his caregiver? If not, then no. If you are aware of the fact that he's a vulnerable adult, and if you are , saying going to be away for a week, I would alert APS. I'm really curious why you think you could be in trouble with the law;has someone suggested that you might?

No, you cannot get in trouble.

I see from your profile that your friend still lives in his own home. Are you a full-time caregiver, or a neighbor/friend to pops in to see that he is ok?