milo,
1) The maid will be permanantly stationed at mum's place even after BB is born cos i dun like a stranger to be at my own place plus i am staying with mil. So even if i take BB home every night, maid will continue to stay with my mum.
2) There is no really legal regulations on this, but you must make it clear to the maid in the first meeting that she is staying at your mum house for weekdays and back to your own house for weekends cos you are working. If she is not agreeable, then dun hire her. This arrangement works our fine for all my colleagues cos it is better to leave the maid with parents than leaving them alone at home.
3) Expenses wise, yes, it will be heavier. I am giving my mum about the same amount as you too, so plus the maid, total expenses will be about $1k plus. You will need to discuss with your hubby about the increase in financial expenses as it is a 2 years committment, if he is taking care of all other household expenses/bills and BB's needs, then it should work out fine. The maid do not have much daily expenses that you need to spend on. She eat whatever we eat, use our shampoo/body form. Only thing is the sanitary pads that my mum gets her to buy on her own. Cos it is CNY, so she have some angpow to spend on.
Alternatively, do you have any siblings that is going to put the kids at your mum house as well? You can talk to them to split the cost of getting the maid?