@vessmith,
No idea what country you're in (or state if it's the US).
He should contact a lawyer to see about assuming full custody/care. If the mother is competent, she can make out a power of attorney to only your friend. If she isn't, then your friend may need to sue over this.
As for a place for her, he can ask her primary care physician about options and also ask friends with elder family in care. He should be prepared for her to pay through the nose and probably lose any savings she's got left. And it won't do any good in the US for her to just give him all her money, as there is a 5-year (it might be 10 these days) look back to prevent that very thing.
I think priority one is getting Mom out and safe. Worry about evicting the evil son later. First things first - Mom needs to be in a place where she won't be harmed.