I looked after my mum for years. Did her weekly shopping, took her to all her appointments, did her banking, cleaned her house, cooked her meals, did the garden. All whilst working part time and looking after my own home, garden and 2 children. My DH worked abroad most of the time.
I never even bought myself so much as a pint of milk with her money. She never offered me any payment and it didn't enter my head to charge her or to take money from her.
My friend looked after her mum in a similar way only she charged her X amount per mile for petrol, X amount per hour for her time, X amount to clean, X amount to garden etc. She also used to buy herself grocery shopping using her mothers account. This was all done with the mothers full knowledge as a way of passing money onto her daughter.
It has come to light that my MIL pays her DS, my BIL, in a similar way. He charges her to take her shopping, even although she lives en route and he is going to the shop anyway. Or he buys her bread and milk and charges her over the odds. She isn't happy to pay and would be cheaper getting a taxi but doesn't want to upset her son.
I sometimes think I should have had a conversation with my mum about money but I never did and she had a stroke and ended up in a nursing home.