SF has plenty of young professionals who are living with roommates.  I would say a lot of that is driven by the cost of housing, but also because many young people like the community that comes with roommates.<p>That said, I think there is a distinct inflection point in people&#x27;s lives here where they either partner up or just get tired of not having a space that is entirely their own.  The 2nd seems to happen to 30-35 year olds a lot.