How much is enough?

How much is enough to pay a close friend for watching your child 35-40 hours a week? This is someone who never works and is always at home, all their food and bills are paid by someone else. This is strictly spending money. I was told no more then 50 a week. What do you ladies think?  Also this is someone who regularly offers to take my daughter for free just because they enjoy time with her. Also, she is four, potty trained, and would only be eating one meal and snack there.