In order for us to understand what public policy might actually help improve cities with a large homeless population, then we need to understand what assumptions public policy makers might have about the homeless which work against public interest.
It is assumed that many of the homeless are not looking for a job, and that they are lazy. It is true that some homeless are lazy, just like some housed are lazy. However, a large population of the homeless already have a job. Almost all the homeless have spent time looking for work, but gave up after failing for months or years. When you do not have an address, a regular shower, a phone, an alarm clock or an up-to-date work history, then most employers assume that a homeless person is not a good risk as an employee.
(NBC News: Working Families homeless http://rockcenter.nbcnews.com/_news/2012/11/28/15490042-employed-but-still-homeless-working-poor-say-homelessness-can-happen-to-anybody
Why is Employment Difficult for the Homeless? National Coalition of the Homeless http://nationalhomeless.org/issues/economic-justice/ )