T.S.
Do you have a friend who might do it with that kind fo flexibility? A few years ago I took care of a friends kids with that kind of schedule. It was $20/day per child, but as long as she gave me her schedule in advance then I was fine with the days off and her not paying for days they didn't come. If she cancelled on me last minute she still had to pay me though because I had them on my schedule and I had already scheduled my day around her kids coming. One downside because she won't be making much she will probably want to be paid in cash and you not to claim it on your taxes. If she is going to give and be flexible you will have to be flexible with understanding that too. Good luck!