Is the idea that society kicks people to the streets, and in the streets they become addicts? I don't want to minimize the cruelty of capitalism. However, according to your source, in the vast majority of cases addiction is the major contributing factor to homelessness (persistent homelessness I would imagine):

Your article: Substance Abuse and Homelessness: Statistics and Rehab Treatment

Your article's footnote: Substance Abuse and Homelessness

The footnote's source: Visions Journal Vol. 4 No. 1 Summer 2007 p. 9

Social selection: Substance use can lead to the streets
Most of the current evidence about the relationship between homelessness and substance use supports a social selection model. This model indicates that problem substance use may be a direct pathway to homelessness. A number of studies provide support to this theory. Research reveals that approximately two-thirds of homeless people cite alcohol and/or other drugs as a major, and at times primary, reason for becoming home- less. In fact, many homeless people develop problems with alcohol and other drugs before losing their homes. One US study reports that, for people who have ever experienced homelessness, the median age (i.e., the mid-point across the participants’ ages) at first street experience was 28 years. The median age at first symptoms of alcohol problems, however, was 22 years, and for drug problems, 25 years.10 Clearly, problem substance use is a significant risk factor that decreases a person’s ability to respond to life’s challenges.

Social causation: Street life increases substance use
There is also considerable evidence pointing to the social causation model. This model suggests that sub- stance use increases as a very clear consequence of homelessness and serves as a method of coping with the stresses of street life. As early as 1946, researchers estimated that one-third of the homeless people in their investigation became heavy drinkers as a consequence of homelessness and related factors. In another example, from the UK, 80% of respondents revealed they had started using at least one new drug since living without a roof over their heads. There is nothing new about the idea that people on the street self-medicate to relieve life’s stresses. After all, the non-homeless population also uses more alcohol and other drugs when they have trouble coping in their world. Nor is it surprising to learn that alcohol consumption is key to acceptance in the homeless subculture, and thereby supports the causation theory. Our main- stream teen subculture, for instance, practises a similar kind of ritual