The longer version: 10 years ago, we sold our house, and Mom sold her house. We pooled our money and together we built a house designed for caring for her. The house is in our name. We charge her a modest amount monthly for utilities and all the routine expenses.
A bit about her: She's 85, legally blind, and has mild cognitive impairment, which is slowly worsening. She is also a scam victim, so my wife has POA. And, she's a low-level hoarder.
Mom is a miser from hell. She will not spend a penny if she can avoid it, and highly resents our charging her "rent". She feels like the amount she put into building the house was enough. I could go on, but the point is, we don't think it's fair to us to keep the house in good order without her financial help. She has no problem with allowing anyone and everyone to pay her way though life. To mooch, in other words! She takes advantage of all the local government subsidized programs, and will not contribute to the cause.
The immediate question concerns adding some paving to our driveway, to allow the van that transports her around town to pull off the side of our street out of the traffic, so she can board safely. I spent my entire summer building a retaining wall to support this new addition. I did all the work, and bought all the materials. We think she should contribute enough to finish the paving now that all the prep work is done. In years past, she would comment about how nice it would be to have a space to pull off the road, and I would say "I'll be glad to do that if you'll help pay for it." You would have thought I asked her to cut off her big toe. We had that short discussion several times, but my wife and I finally agreed it was time to do it as a matter of safety for Mom.
There are always things to do around the house. Things that cost money, and Mom thinks that we should be responsible for all of it. We had several discussions about just this kind of thing before we agreed to live together, and we were satisfied that it would work. We didn't have a contract, didn't know we needed one. Now we do, in hindsight.