THE CITY OF MIAMI HAS BEEN working with local builders and developers on an innovative land-exchange program aimed at making a dent in the market's affordable-housing shortage, which a new study claims is spreading throughout South Florida.

The study, prepared by the Florida International University Metropolitan Center, asserts that the area's “explosive” housing boom of the past three years has widened the gap between median home prices and what buyers can afford—in some municipalities by as much as $100,000.

Miami Mayor Manuel Diaz has made providing more affordable housing a priority. In its Model City neighborhood, Miami handed over 98 abandoned or city-owned lots for free to developers and builders that agreed to build homes exclusively for buyers whose household incomes are under 80 percent of the market's median income, as established by HUD. For a family of four, that's $43,300.

Miami's Department of Community Development has been going street by street throughout the city to determine who owns other vacant or abandoned lots, says department director Barbara Gomez-Rodriguez. Owners must register with the city and will be taxed each year until they either develop the property or sell it to the city.

Learn more about markets featured in this article: Miami, FL.