The family realized after interviewing the next candidate what the agency was doing. They offered me the job, but I had found another one already. Parents need to pay attention to the demeanor of the candidate. While reading a biography of Queen Elizabeth's father, the author noted that the nanny to the two royal sons was a lifetime employee. Nannies in many parts of the country work for several years, often until the need for a nanny is replaced by the need for a short after-school commitment, until the parents come home.
Most initial contracts are for a year.
The American nanny is not a third parent, nor a parent replacement. Incidentally I feel that hiring a babysitter should entail the same background investigation as a nanny whether the sitter is a friend of a friend, a teenage neighbor or a classified respondent. There are some questions about the social behavior of nannies, like drinking under age, driving while intoxicated etc. All states require workers compensation. Families that do not provide this can be charged with negligence if an accident occurs on their property.