maybe I'm missing the big picture here, but I don't see why it's actually desirable to have a wide range of incomes within a specific neighborhood. poor people can't afford to shop at {expensive grocery store} or dine at {fancy restaurant}. and wealthy people generally don't want to shop or eat at the places their poor neighbors could afford. if you "urban plan" them into the same neighborhood, now you need two (or more) tiers of every type of business to serve all the residents. at best, everyone has fewer suitable choices of each. at worst (and more realistically imo), most of the businesses continue to serve the wealthier residents, and the less wealthy need to travel away from their "affordable home" to actually get their needs met.