I've just hired one to start after the school holidays and I am so incredibly excited, as are the kids. Heard so many good things about it, and when you compare it to childcare costs its phenomenal. Can't wait!

Re the costs - I have seen people with all sorts of budgets and set-ups at different prices - people are willing to negotiate depending on all sorts of factors. I would jump onto au pair websites, read some profiles from families and get some ideas from there.