Maybe we could train an army of specialists to refurbish and modernize these cities with high speed internet, excellent public transportation, and carbon-free power sources.
Then we could offer them up for homestead, with free water and utilities for a year, no rent or mortgage for two, first dibs to the people actually doing the reconstruction.
Those who don't make the transition to self-sufficiency in two to five years would be offered more conventional publicly subsidized housing and other opportunities.
All the resources required to do this, money and manpower, could be diverted from our overheated military budget.
I don't think it would take a great fraction of those resources to nearly eliminate homelessness and wage slavery in the U.S.A., and it would also create a more welcoming environment for immigrants and refugees whom we need to prevent demographic senescence.
That probably sounds too much like communism to some people. It's actually an investment in our future.
Libertarians like to believe such progress can be accomplished by the "invisible hand of the free market," but it's not happening. Gentrification is not the same thing. For every "winner" in the gentrification game there are more losers -- mostly lower income people who are driven away by high rents and evictions.