Factor in the cost of gas plus you know you're also buying your own meals (and probably the kid's too), and you're making less than $100 for 40 hours of watching a small child. And what do you want to bet it'll soon turn into the mom wanting the sitter to stay late because she needs to run errands after work...and most definitely, as soon as she gets comfortable, that offer to "wash your clothes for free" will turn into "while he's napping, do some laundry for us". You know, because she's not going to pay anyone that $2 an hour just to sit around scrolling through their phone while the child is down...