If elderly mother moves in with daughter, should mother contribute to household expenses? How much?

OH my. In my opinion, yes she should contribute. My rule, Adults don't live in another adult's home and not contribute . (That goes for grown children bouncing back home, but that is another topic!) How much, phew that is a difficult question. Certainly, room and board. All of Mom's children may be asked to suggest what is appropriate. Will the others be contributing to the care giving responsibilities (Time/talent?) If daughter is the only one doing things, you should consider a personal services contract. This should include increases as work increases or family should be willing to hire outside help as things develop (using Mom's resources). Trust me and others, with dementia, the care ultimately is constant. By including the other sibs now, tension may be eased later. Good luck