I have a live-out helper myself. But you should note that, technically, it is illegal.
Personally, I think this law is unfair and discriminatory. I don't see why a Filipina maid is not allowed to have her own home -- and her own place to go on a Sunday instead of hanging out on an overpass like a homeless person. But the law is the law. And while I have never heard of my prosecution in my 15 years in HK, you are taking a calculated risk.
In HK, people will tell you you "need" a live-in maid with a newborn, because that is sort of a societal norm. But almost nobody has 24-hour help in the West, and mothers survive just fine! (I did, breastfeeding a newborn exclusively, and then being a working mom).
Here are the pros and cons
Pros
* You have more room at home. I sometimes work from home, and appreciate not having to convert my home office into a maid's room.
* You have your privacy -- my husband and I like to have a glass of wine and a quiet chat each night after the baby is asleep and the helper is gone.
* Your helper is probably happier -- and that also makes her a good worker. I have many friends, mostly local, whose helpers are worked all day and night, and they tend to have tensions, probably due to stress, fatigue and just never getting away.
It's good for my helper to simply have a full day off, from Saturday night to Monday morning. Live-ins, with nowhere else to go, often spend their "days off" around their workplace. Or they end up sitting outdoors somewhere, like a park or streetside.
Cons
* You are taking a (small) legal risk
* It costs more. We pay our helper $4,000 salary + $3,000 to cover her rent and food outside. If she lived in, she'd just get the $4,000, though your grocery costs would go up a bit.
* If you're responsible, you will have to be involved in finding her a safe, clean place to live. Some of the boarding houses for helpers are not good. We personally put down a deposit on a small flat for my helper and her two friends to share -- but if anything goes awry, like her roommates don't pay their share of the rent on time, or there's landlord trouble, etc -- you have to step in.
* Sometimes, when we had some tough nights and I didn't want to bother my husband (who gets up very early for a tough job), I wished my helper were there overnight. But she's always been great to occasionally spend a night -- like when baby was having sleep troubles and I was exhausted. We just pay her a bit of "OT"
In the end, we're still happy with our decision to have her live out. Hope that helps!