Protect existing affordable housing.
Create more and varied kinds of affordable housing, through more aggressive inclusionary zoning, support for community land trusts, and better public-private partnerships.
Provide tax relief to homeowners who are "house rich, cash poor."
Reinvest in public housing.
Tax big developers and speculators; use this revenue to subsidize affordable rentals and retail.
Require universities to provide affordable housing to grad students and postdocs.