Giving housing to the homeless is three times cheaper than leaving them on the streets:

The most recent report along these lines was a May Central Florida Commission on Homelessness study indicating that the region spends $31,000 a year per homeless person on “the salaries of law-enforcement officers to arrest and transport homeless individuals — largely for nonviolent offenses such as trespassing, public intoxication or sleeping in parks — as well as the cost of jail stays, emergency-room visits and hospitalization for medical and psychiatric issues.” Between 2005 and 2012 the rate of homelessness in America declined 17 percent By contrast, getting each homeless person a house and a caseworker to supervise their needs would cost about $10,000 per person.