It depends on the child but I would honestly say 2. I sent mine for 3 hours a day.
I got to working from home doing what I do so I did it around that.
Career is important, I really need to get back into it since neglecting it to be focused on my child and that has its own drawbacks, but if you're going to choose one I would choose the child every time.
I'm not seeking a job where I can mingle with people instead of kids all day. I have been working but it's been a bit difficult and we're not well off. Now she's going into a bigger year with more after school activities I'm looking for roles but I'm not young and it's a big career gap but I believe it's possible and even if it wasn't, I spent those years nurturing my child and the bond we have is brilliant because of it.
I can't compare it to a different situation as I've only had one.
I wouldn't send before 2. I'd be doing groups and parks and soft plays. They're funny places, you should find a good one with a nice cafe, maybe join some home ed groups or local groups or a church to gain a group you could organise things with. (you can get in with the home ed groups as your child isn't in school) they can be an interesting bunch and I've made some good friends that way.
When I look back on the years she was a baby I'm so glad I was there for all of it. It creates a secure attachment and they don't mind leaving you when the time comes. Mine walked happily into nursery and seemed to enjoy every minute. She's very good at making friends, perhaps it took her a few weeks to settle in since she'd never been in a nursery, but we did spend the first year in baby groups and the second with other groups including kids and adults so she wasn't isolated.
But I am somewhat isolated. Not having a job, every single school run, appointment, entertaining friends, constant tidying and cleaning. I cannot wait to get into an office or something!
Perhaps your company will give you more time?
Or is there the possibility you set yourself up in whatever it is you do so that you can do it remotely, independently, contractually, in a role that is 100% remote, or retrain?