I'm not sure it's actually a bad thing to let people work for free if there's a reason they honestly want to. As long as they're not trapped in some manner.

Plus it's tricky when it comes to something like 'watching children part of the day'. It wouldn't be considered labor if it was a family member doing it, whereas stacking shelves certainly would be. If I'm letting someone live in my house, why should it matter if they're family when it comes to having them do chores?