Hey ! I'm sorry this is going to be a long post ! I'm gonna talk to you about my experience. But, you have to understand that my experience is not something that is BOUND to happen, but I just wanted to say that it does happen.
I'm French, and I left France in 2013 for Australia to be an Au pair. I mean, it's REALLY a great deal. You have free room, food, and get some pocket money as well. But in exchange you have to take care of the kids during the week, sometimes during the weekend as well (but the terms have to be discussed with the Host Family.) and when the parents get home, you're usually free to do your own stuff (explore the city, etc...).
I found my family through a website, and after a few skype video calls during which we talked about what we both wanted, we decided that we were a good match and that's how I went to Australia.
At first, everything was great : they came to pick me up at the Airport, show me around the house, around the city, explained to me what they wanted, and so on. The first few days I was still with my "host mother" at the house just for me to get used to the kids (2 little girls, one 8months old and the other 2 years old). Weeks passed, I started my babysitting. I was taking care of them from 7am until 6pm sometimes. I would cook them food (obviously), go to the park with them, the library, the waterpark, everything that I was able to do. It was pretty hard to do a lot : the baby required a lot of sleep and their naps weren't matching : when the baby was sleeping the 2yo would be awake, and when the 2yo was sleeping, I was taking care of the baby.
After a few months, the mother started to reproach me a lot of things : I wasn't doing enough. She was saying that I was spending all my day home, leaving the kids in front of the TV, and that's about it. She wanted me to write down a MENU for the 2yo to eat. She wanted me to go, just in one day, to the library, the park, the waterfront, and why not somewhere else in the city. She wanted me to create activities for the kids. She wanted me to do SO MUCH. MUCH MUCH more that I could handle even though I was already trying my best to please both of the kids. The thing is, you also have to do with THEIR way to educate a kid. Sometimes, the 2yo would get so angry that she would just kick me, and I wasn't able to even say "it's not good to do that", because "she's just a baby!".
Anyway, long story short, I really killed myself for them, I tried to please them, so much that at the end, after 4 months in Australia, I hadn't even seen 10% of the city I've been in. I wasn't going out, didn't have any friends, I spent all my time at the house with the kids. I didn't get any culture. My pocket money was really thin. I was really, really depressed. And then, the mother started to complain about me to the neighbors. They liked drinking (nothing wrong about that, but) and usually would invite their friends over to drink with them. And often when she got tipsy, she would say stuff like "I don't know why I'm paying this girl, she's just spending time here in front of the TV, and I think she's trying to get into my husband's bed, she's a bitch and I'm wasting my money!". HONESTLY I cried so much that night, and that was enough for me. Everything she said was obviously wrong, even the neighbors told me not to pay attention, but it was just... awful. Thankfully, I met a boy a few week earlier, and I talked to him about my problem : the same night I left this house with my luggage and I never went back. I stayed at this boy's house until I found a new job.
So here's my advice : BE VERY CAREFUL to the family you're choosing. BUT. Even if my experience was the worst and even if I know that I will never, NEVER be an Au Pair again, I'm still super glad that I did it, because after these terrible 4 months, everything else was just paradise. And I would never have been able to go in Australia if it wasn't for my Au Pair job (they paid for my visa and let's be honest, free home, free food is a great deal to begin with). I have many friends that had great experiences being Au Pair, so don't take just my bad experience as a given. You might enjoy it and find great people! Just be careful and SIGN A CONTRACT, (I didn't) or make sure that you agree to all their conditions beforehand.
Good luck ! (and sorry for this longgggg post )