San Fransisco has a lot of land zoned single family.<p><a href="http:&#x2F;&#x2F;www.sf-planning.org&#x2F;modules&#x2F;showdocument.aspx?documentid=9016" rel="nofollow">http:&#x2F;&#x2F;www.sf-planning.org&#x2F;modules&#x2F;showdocument.aspx?documen...</a><p>You could easily rezone and up the density by a factor of 4 or 5.