Do you want to be a sitter or a nanny?

Baby Sitting - Sitters' Registry 

A baby sitter works temporary baby sitting jobs as they come available.  You work around your schedule, only accepting jobs that you can work.

Nanny - The Nanny Network

A nanny makes a commitment to one family, either full or part-time, usually long term. The schedule is agreed upon upfront, so the nanny knows how many hours she'll be working and how much she'll earn.