One of my friends does nanny share and can work in his basement. That would work well, but you still have to be in stealth mode around the kiddies.
- Newborn to ~6-9 months: not mobile, and not too demanding either (especially early on)
- 6-9 months to 3 years: mobile and constantly trying to hurt themselves
- 3-5 years: mobile, mostly safe, but not understanding what "no" or "I'm busy right now" or "I'm on the phone" or "I need privacy" means; also not napping anymore, which means you lose that daily couple hours of bliss
- >5 years: gets progressively easier as kids begin to get independent and (somewhat) reasonable
Of course, this timeline is different for every kid.
We have four kids ranging in age from 1-7 years old. I work from home, but rarely am I in charge of taking care of the kids (right now, for instance, my mom is watching them while my wife runs errands). On the occasions where I am solely responsible for them, I consider any work I get done to be a bonus.
Toddlers, on the other hand, are little balls of pure energy that get into anything and everything they can touch.
It was hardest for me around 3... my son just wanted to play all of the time.