As part of the largest US attempt at a public-housing makeover, some residents are now being required to work. CHICAGO - Driving down Halsted Street in Chicago's Near North neighborhood, the contrasts are stark. The collection of new red-brick three- and four-story apartment buildings that make up the mixed-income North Town Village - all with tailored landscaping and individual balconies - eventually gives way to old Cabrini Green high-rises, ugly concrete behemoths that sometimes have more plywood than glass in their windows. The move toward mixed-income communities - an integration of public, affordable, and market-rate housing - has already made...