My kids are "home alone" fairly often these days. Often Fiona prefers to come along with an adult, though she's increasingly happy to be home. And I've never paid Erin to be responsible for her siblings when I'm away.
Recently I've heard it said that it's unfair to expect eldest siblings to be responsible for younger children without paying them as you would an adult or older teen from outside. I've heard adults talk about having cared for younger siblings and resented that it interfered with their after-school activities and down-time. They mentioned finding their siblings a huge burden.
I still don't pay Erin and while I'm sure she wouldn't give back the money if I started paying her (she does have a serious iTunes addiction, after all), she certainly would never expect to be paid.
For a bunch of reasons.
First, a few hours a week does not eat into Erin's down-time or extra-curricular activities. Homeschooling gives her loads of time. Her late evenings and weekends are not precious in the same way that they are to schoolchildren.
Second, homeschooling has helped create an inter-sibling dynamic that is comfortable and respectful and that works. Erin does not find being with her siblings a burden any more than being with her parents is a burden. (Let's not go explore that last scenario any further, okay?)
Thirdly, one of my expectations is that being part of a family means contributing to making that family work -- without pay. I don't get paid to do laundry or carry in the groceries, and neither do the other people in this family. The kids understand and they contribute too. Sometimes that means setting the table, or picking up dirty laundry or feeding the chickens. And sometimes it means preparing lunch for your littlest sister while your mom and dad are away.
The biggest reason she's not paid, though, is that when we leave the kids home I am not asking Erin to assume an "in loco parentis" role. I am asking her and her siblings to behave in an appropriately responsible manner, to work together in ways that make the experience safe and enjoyable for all of them. Obviously if there is a serious safety issue or unresolvable conflict, she would need to exercise leadership commensurate with her age, ability and role in the family, but I am not asking her to be in a position of authority over her younger siblings -- I'm not putting her "in charge." Instead I'm saying "you guys need to work together so that this is safe and enjoyable for all of you."
And there's one final reason why I don't pay Erin to babysit her siblings when I work my clinic mornings is that, well, it's that she's usually asleep the whole time I'm gone. Hooboy, it's amazing how the teen shift in circadian rhythm has compounded her night-owl tendencies!