I have found people for this position on Craigslist and Care, and through word of mouth. The best two I've had were a college student who was just a dynamo -- could do anything, was super efficient, also great with the kids, and then, when she got married, her mother-in-law took over. She is better with the house (can see what needs doing without instruction), and fine for helping with the kids. She gets tired if she has a full day of kids by herself, so I don't ask her to do that, but if the nanny is out and I need the morning to work, she can do that.