I have my doubts.
If the person was taught properly, yes. I know someone who worked in the house of Rav Oshry in the Bronx and she was trustworthy in keeping a kitchen kosher.
Absolutely, it all depends on your supervision.
We’ve had the same cleaning lady for 12 years. Before Pesach she brings additional help (daughters, sisters, etc….varies each year).
They clean under Mrs. CTL’s or my supervision using only cleaning supplies and tools provided by us.
Of course you can! Just don’t let them clean the kitchen or supervise them properly.