The two staircase rule increases costs, but not by that much - any place that allows building housing doens't have a homeless problem. That isn't to say there are no homeless people - there are many - but they are homeless because of other issues (mental). In California the homeless often are otherwise normal people who cannot afford a place to live despite the ability to work a job. Where I live you can rent a new two bedroom apartment in walking distance of Burger King that pays enough to afford that apartment and leave enough leftover for food - it won't be a great life, but you can live on one income (and since most people live as a couple that second income can buy some nice things)
We should get to reap the benefits of improved fire and personal safety and build more housing.