Homeless people, by definition do not have a fixed residence, but that is where the simplicity ends.
“A 2008 survey by the U.S conference of mayors asked 25 cities for their top three causes of homelessness. Drug abuse was the largest single cause of homelessness for single adults reported by 68% of cities.”
Homelessness & Substance Use Disorder Treatment (2010)
Drug abuse and homelessness is a sort of chicken and egg debate not only because of its age and importance but because either can result in either one i.e. someone can become homeless as a result of chronic drug use or a homeless person can become dependent on drugs as a result of homelessness and being exposed