The problem you are describing is a result of ghetto-ization, both self-imposed (people like to live near their "fellows") and externally imposed (lack of a wid

The problem you are describing is a result of ghetto-ization, both self-imposed (people like to live near their "fellows") and externally imposed (lack of a wide range of property values in an area leading naturally to income-segregation, with recent immigrants likely to end up stuck all together). If you solve the problem of income-segregation by somehow generating a city where rich and poor live side by side, then I think you go a long way to tackling the source of ghetto-formation, both for immigrants and the local poor. I have seen several cities where this has been achieved, though I have no idea why it occurs in one area and not another. I have a suspicion that it is tightly related to the density of development. A city with lots of skyscraper apartment blocks (both fancy and simple) can fit so many people in such a small area that even if the rich and poor live in different buildings, the buildings may be so close together that they share the same services (schools, hospitals, restaurants, etc). As a concrete example, I live a short 5 minute bicycle ride from a friend of mine. My 8 story apartment building has about 24 units, all of them relatively modest. My friend lives in a million dollar condo in a building with probably 30-40 units as well. This is in the very heart of the city.