Cities could convert some neighborhoods into learning districts for personal, professional, and entrepreneurial development. They could provide a curriculum for development supported by the infrastructure (buildings, technology, services, mentoring, and community) within the district, and further provide certain non-financial "commitments" that families in these districts must meet to stay there. People would "win" or be granted a location in the district for 2 to 7 years depending on the development challenge and goal (DUMBO did this to get started). They would be provided things like office and meeting spaces, field trips, advisory boards, mentors, courses, market research resources (if applicable), etc. in exchange for showing metrics of growth and a percentage of return in new services for the districts (come back and mentor/be a professor), or a percentage of profit.This is part 14 of a continuing brainstorm on the future of cities, inaugurated at the CEOs for Cities Velocity conference in September, 2009. We'll post a new idea each day until we run out, at which point we're counting on you to come up with something smart. Do you have a good idea for improving your city? Add it in the comments below, or tweet it to @GOOD with hashtag #cityideas-we'll publish the best ones. Monday's idea: Free-agent Portfolio.