My friends want me to watch their kids for free: Thoughts?

I was wondering if you could give me some advice. I just moved in with my friends, and they have three kids because they both watch. I’ve been in charge of watching the kids now they both want to be a truck driver, so they would be gone for three weeks at a time I would be responsible for their kids full time, and even when they are here, I’m still responsible for feeding them and bathing them, but they don’t want to pay me anything, and I was wondering is it wrong of me to say demand at least some pay

They should def be paying you or they should find someone else to watch their kids