Housework and childcare are two different things, finding someone who is good at both is next to impossible.
If you need a cleaner, get a cleaner.
If you need childcare, get a nanny.
If you want to help a young foreign person learn English language and English customs, then get an au-pair. In return they may do some washing up, ironing, and may entertain your children for an hour or so if you are lucky.
INMGBSLM - Work out why you need an au-pair, what tasks you want them to do. Then see if that is something an au-pair would actually do, or if you are better off getting someone else in for a few hours to do one thing - such as having a cleaner come in for 3 hours or so once a week.