Help ladies!

So I'm about to start baby sitting my 2 little cousins that are 2 and 3 because their mother is going back to work since my cousin (their dad) is currently in jail for a while..

She asked if I could watch them Monday-Friday for 8hrs. She's asking me how much would I charge her. I dont want to charge her too much cause she is family and I know she needs help. So if you were in my situation how much would you charge her?