I think that as others have said, it depends on why and their personal circumstances.
I think that if effectively healthy and able bodied, then they need to be able to continue to live their life and you also yours. I'd probably have a large family calendar, with every with a column and same for meal planner. Have an agreement who cooks when if sharing the cooking. One of the things I've noticed with family we care for, is they have often lose some of their autonomy over little things like what they eat as often they will go along with what's offered rather than say I really fancy xyz. So I'd keep that in mind.
If she's going to primarily be at home, I'd try not to expect she does all household activities, but equally she needs to take some responsibility.
Don't fall into you say doing her laundry etc when she first moved if you don't wish to set a precedent.
Will she have and you have your own reception areas so that if you just want to sit down and not talk to anyone and watch crap TV, you can.
A little bit more background and I'm sure that you'll get some more suggestions.
Finances will be dependent on whether she's contributing to the house/mortgage/deposit and has an interest in it.
I would perhaps set an amount for utilities etc, and then review after 3 months. Or take the attitude of these are the bills divided by 3. But if children are in the house that complicates things and I wouldn't want for her to feel taken advantage of. Unless of course she an annexe with separate meters etc. I'd also take into account if she'd previously be receiving housing benefit that her level of income will be substantially reduced and she's unlikely to receive without a whole palava in your house.
You may also be able to benefit though from her pension credit if she receives, if she's named on utility bills and likewise council tax reduction, but if you have an oh, not. Though you would get a discount if you're converting a room specifically to meet her disability needs.