What exactly does an Au Pair do and what does one cost?

Christian Lheureux wrote:
>
> Along the same line, our household will have an au pair from Montreal,
> Quebec, in a few weeks. She was 6 months old when I landed in Montreal back
> in '82, and she is now a young adult, beyond any doubt. And she probably
> does nicely fit what John wrote, with a few additions of my own :