Salaries range based on years of experience, demands of the job, location, and whether you want to be a live-in or live-out Nanny.
Live-In Nannies - Salary ranges from $350 - $700 per week
Live-Out Nannies - Salary ranges from $400 - $800 per week
I am a graduate of Northwest Nannies Institute, and this is current info from their website. (http://www.nwnanny.com) This is for a full-time nanny, and they do placements all over the country.
I have also worked in daycare, and it is a considerably cheaper option. At the weekday school I once worked, for 1 child it is $160 per month per child for 5 days of the morning session (8:30-12:00).