Granny flat arrangement
I am really interested in people's points of view on this issue as to what you believe is a fair arrangement. I care about the people involved and want to make sure that nobody is taken advantage of, and that a fair result is achieved.
A friend (in their 70s), whom I will call 'Mary' just to make it easier for my post, is planning to sell their house, after her husband recently passed away, and move into a granny flat at a property owned by their child Bob, and Bob's partner and child. Initially this is for around 12 months but may be longer term. Mary will be selling her house but probably won't get much for it, and is not exactly flush with money. Part of the reason for doing this is that Mary will be taking care of Bob's child in the mornings for him before school, and will pick the child up from school and look after them until Bob and partner come home from work (I believe Bob and partner both work roughly business hours). There is no formal plan of more childcare than that, but past history suggests it is likely that Mary will be asked to look after the child fairly regularly if Bob and partner go out as well. I don't believe there is to be housework involved, but I think it's likely in the course of looking after the infant-schooler Mary will wind up doing bits here and there.
Mary will be moving to this flat from out of town, and is still very active etc and will definitely want to get involved in a few things for herself when she moves residence. She currently volunteers sometimes, and works very occasionally. Needing to be available for her grandchild's childcare before 9 and after 2:30 on weekdays will obviously have an impact on what she can plan for herself.
With all the above taken into consideration, what do you believe would be an acceptable arrangement financially in this situation? Should any money be changing hands (Bob getting paid rent, or Mary being paid for childcare etc), and if so, how much and to whom? Should there be any other kinds of benefits (meals, electricity bills included etc)? Mary will have her own car.
How do you believe they should set things up so that it is fair for all involved, and nobody is being taken advantage of, and obviously also recognises that this is family, not strangers, making this agreement?