Williamsburg, a first-world Johannesberg?

Excessive migration to urban centers from the countryside has been a recurring problem for many countries, especially in Africa and South Asia, because the influx of poor strains urban infrastructure, looks bad, and causes growth in the informal sectors of the urban economy. How to fix this problem?
1) close off the cities to migrants?
2) fix the root of the problem-- rural poverty
or, my favorite
3) create suburban "townships" or camps where migrants can stay at night so they do not form slums or dirty the city landscape. Prime examples: Johannesberg, South Africa and Williamsburg, VA