Granted, the nature of this site means that we will always hear more about the bad cases. Someone from a functional family with a good caregiving situation would have no reason to post here.
But. There are A LOT of horror stories. So many that I think they are more or less the norm.
I'm inclined to think that no one should ever take up significant caregiving responsibilities without having full PoA, and getting whatever inheritance they expect UP FRONT. And no one should quit a job to caregive unless their financial situation truly enables them to do it safely.
And that's just the financial angle. If the family dynamics are such that you, the prospective caregiver, are not likely to get support from relatives (or worse yet, be attacked and manipulated by them), DON'T DO IT. Relative should be told by the care-receiver, in writing, that the care-receiver's assets will be used to fund care, and that IF there is anything left, MAYBE they will get an inheritance. But they are must keep their face-holes shut about it if they want to get anything at all.