It's a great idea (elderly have the space, young people have the time), but I wonder how many elderly will do it in practice.
My doubts come from watching my in-laws recently go through the process of in-home care after a stroke.
My wife's grandmother had a stroke and needed in-home care. She and my wife's grandfather live in a giant exurban house, probably 3500sqft with a full, unoccupied mother-in-law suite built into the finished basement. My father-in-law's idea was to find a nursing student to live in the house rent free, and to pay them a reasonable hourly rate for providing care. His logic was that the unoccupied space was basically a sunk cost with no real marginal costs for occupation, so better to have someone living there and acting as extra eyes and ears in the house than not.
He brought the idea to my wife's grandfather, who for reference is in his late 80s and is a first generation immigrant.
He was appalled. His math was that he lived in a beautiful house, so providing anyone a room should be at least $1000/mo taken out of their paycheck. Pay them $15/hr for a couple hours a day, and they should still be paying him about $500/mo to live and work in his house.
You can see how this was never going to work. Instead of doing the common sense thing, in the end they paid tens of thousands for professional in-home care on an hourly basis.
On the surface, a service-for-rent arrangement would make all parties better off. In practice, I imagine often times it's going to run into snags as the different parties come to common terms about what their space or time is worth.
