From my experience, this is incredibly uncommon in the northeast. I only know one couple like that in NY, and she has a large enough trust fund that neither one of them really needs to work at all. Every other couple with children that I know actually living in the cities are 2 income households. The same holds for everyone I know in Boston.
I've already qualified my comment, and both of us were discussing personal experiences.
If you'd prefer to discuss the general population instead of trading personal experiences, here is some historical data from pew, as well as the most recent report from the BLS:
This shows that my experience is closer to the general population than the experience I responded to. I'd venture a guess that the distribution of that ~62% isn't uniform across the country and is likely weighted by cost of living (which is likely why our experiences differ).
