We are new to having an au pere but I can tell you it is the best option we have found! We use Cultural Care Au Pair. Things that help you decide if it is for you: Do you have another bedroom for her/him? They are required to have their own room and can't share it with a child. Do you want the flexibility of moving the schedule around each week? They can work up to 45 hours per week, up to 10 hour a day, and need to have a full day off each week and one 5 hour day. They also need one full weekend off per month and vacation time. I found it is great to have someone here to help my husband at night put the kids to bed when I must work, or have her watch them at night so we can have a date!
The drawbacks are that you can get someone who you don't connect with, who is immature and is like having another teenager. You may find that you have to really lay out your expectations upfront and it can seem like a lot of work, But, that said, I think it works out great more times than not!