It can be difficult to get a temporary work visa to work as a nanny, but not impossible. The processing time depends upon where you’ll be working, but in general you should count on it taking at least 9 to 12 months. There is a special, shorter application procedure if your potential employer is currently in the US with a temporary visa AND you previously worked for the employer overseas. Please have your employer contact me for further information.
Attorney Edward Weiner
http://www.immigration-aux-usa.com/