It depends how often you want her to come. If you want to hire an ayi every day, it'll cost you anywhere from around 1800 to 2500 rmb a month. For someone who just comes twice a week to clean the flat, 500 rmb will be more than enough.

i was told twice per week would be 400 a month in Chang Ning area of Shanghai.  But i dont have her yet so it may be a bit more.