[romwell]

I just want to add that the rent doesn't scale proportionately to number of bedrooms.

E.g. a 1BR in San Jose where I live goes for $2100/mo, a 2BR goes for $2400 (obviously, it's different everywhere - a friend of mine is renting a room in SF for $2K+).

It makes sense for a couple to get a 2BR even on a single income if it's good enough (and usually, once you can afford spending $2100/mo on rent, you can afford $2400 too). For 15% increase in rent, one gets the ability to e.g. comfortably invite friends/parents from out of state for a couple of days.

Of course, single-income no-kids couple does not look immediately look like the norm these days; but once you think of it, there are plenty of situations other than children that make sense for such a scenario: one of the partners might be in school / looking for a job / changing fields / being involved in something that doesn't provide a stable salary (arts, entrepreneurship) / did I mention start-ups? / etc

[ironjunkie]

This is also because in San Jose// San Francisco, most of the population is a single twenty or thirty something that only need a 1Bedroom. The demand for 1BR is therefore absolutely huge compared to 2+BR