When I started I used to offer 24/7 care and charged $10/hr outside daycare hours when I did not have any idea of the market and how much parents were willing to pay.

In this area most of the few providers around are still offering care outside business hours and they charge from $10 to $15/hr.The rate around here goes from $40 to $50. If I do it again I would like to be well compensated. Teenager babysitters (the ones that go to parents' homes) could charge up to $12/hr depending on experience and most experienced nannies could charge up to $20/hr. I think I would recommend you to check at Kijiji or Craiglist in your area and see how much on call nannies are making since they would be offering a similar service so you don't sell yourself cheap or overcharge.