I think Singapore is really ahead in the affordable housing front. They have nice places where people actually want to live. I am not sure if and how it is possible to replicate this on a larger scale.
California has requirements that developers have to designate certain units for low income. However, for larger developments, they found a loophole, where multiple developers pool all of these units and put them in a separate building.
I think it completely beats the purpose. The whole point of this should be so people that hit the bottom don't feel like outcasts. We would be so much better off if we helped them to get on their feet so they can be productive again.
