With a friend of mine, they calculated that they actually saved more money for one person to stay home with the kids than it is for both of them to work and to pay for daycare. But then, they also have twins, so their childcare expense are higher than normal. (Long story short, it often depends on how the numbers come out.)
With my ex and I, we had grandma who lived nearby and was willing to pitch in. So, it made more sense for both of us to work... which we did. (The point here is that it also depends on what kind of family support you have available to you.) Grown kids make for great babysitters also, by the way.
As for your last question, my ex and I have always worked to some capacity, so I can't answer there. However, my friend plans to go back to work once the kids are old enough to go to kindergarten. But that largely has to do with his personality. He's a go-getter type, and really wants to be working again. (And the point to take away here is that, this also depends on the individual personalities involved. Some would rather be a stay-at-home, but some would not.)