There are many factors that play into the cost of a nanny. Some factors include how many hours a day they work, how many children they care for, what responsibilities they perform while they are working, qualifications, and more. It is not uncommon for nannies to be paid an hourly rate bi-weekly or once a month. For a live-in nanny who works every day, it is also possible to agree to pay on a salary basis. Different nannies come with different rates that they usually choose themselves.