I’ll answer this because my son was a live-in nanny for three different families. He was American/they were American, so the kids didn’t get the advantage of a second language. But he was an excellent nanny. During college he worked for a professorial family. Their deal was that he worked 15 hours/week (with 3 very young kids) for room and board, and beyond that, they paid him per hour.
The classic “con” is that the au pair’s youthful adorableness is so titillating that one of the parents falls for her or him, and all hell breaks loose.
The other classic “con” is that s/he’s terrible with children but you aren’t smart enough to give her a trial run. So, do that.
A classic “pro” is the fun of having a person in the house who’s between your age and the kids’, and the practice you get in finishing up the raising of a young adult. And, if
she’s foreign, the likelihood of having people in another country to visit later.
Good luck. Could be great. Will be challenging too.

Con: Finding a good one (which means finding a REPUTABLE agency)
Pro: Havig a good one.

I was a long term nanny for an infant. I think that it is a great way to have your child cared for. But here are the pros and cons I came up with.

Pros: getting to know the person taking care of your children on a personal level
knowing that your child is the focus during the day (care is not divided between many children)
having someone really get to know your child, and be able to be there for them when you unable
your child can have wonderful experiences when with one adult

Cons: feeling jealousy towards someone becoming extremely close with your child (I found this with the mother of the infant I nannied for, she definitely resented the relationship I developed with her baby, she eventually worked through this, and we became quite close)
your child can be somewhat isolated when they are with just one other person all day, they miss that kid to kid interaction
definitely finding a good one is tough——I would not recommend an agency, I think that it is better to do the legwork on your own.
making sure the person can make the commitment for AT LEAST a year, so as not to disrupt your child (and your) lives too much.

i had a live in nanny from when i was 2 till i was 13 (she didnt babysit me at 13 she was more of a live in maid) but it was the same lady i loved her deeply and she taught me a 2nd language so i have had a good experince with it, i have no idea how my parents found her though.

Shilolo
Go for it!

An au pair girl comes from one country to another to live in a family, and do some housework. A nanny girl (or maid girl) is employed by the employer to do housework, and many of them are live-in.