I've known a lot of homeless people. Ferret and Clara come to mind as the most pertinent examples. There seems to be common themes. Substance abuse and/or mental illness are the most glaring causes of homelessness. I was homeless mainly because I was an alcoholic who couldn't get sober no matter how hard I tried. I lived to drink and lived for the next drink. I couldn't afford rent with my drinking problem when confronted with my paltry income. I made a conscious choice to be drunk and homeless, than sober with a home.
Another thing I have noticed with homelessness, is the petulant and childlike qualities a homeless person will exhibit. It is as if they never grew up. I've been reading The Homeless Guy for years and it never ceases to amaze me what he will write and say being a 46 year old man. I often have to remind myself that this man is not much younger than my father yet he cannot feed or house himself. Like Clara and Ferret, The Homeless Guy is blown around on the winds of change subject to the charity of others. And get this... he still complains constantly about it. Talk about biting the hand that feeds you.
I saw these same patterns in me as well when I was homeless for six months. Everyone else was to blame. I loved to blame my ex-wife for my problems. Things like... I wouldn't be homeless if she didn't divorce me and took our house. Go ahead and get out the world's tiniest violin and play it. Luckily, unlike Clara, Ferret, and The Homeless Guy, I had a wealthy family who bailed me out when things got too rough. I had to pay a dear price though. I essentially gave up my autonomy and freedom to have a home. My behavior is carefully monitored and controlled by my family through conditioned responses. If I try to go against the set established rules then I am threatened with various aspects of my life taken away. I am sure Pavlov would find me an interesting subject to study much like his dogs.