All it takes to be homeless is not being able to afford housing, drugs or mental illness are not required. You really think all it takes is "choosing" and housing will appear for you?

Also, drug consumption and mental disorders is very often a result of being homeless. Try having bad sleep in your comfortable home for a few days in a row and see how quickly your mental stability deteriorates and how many bad decisions you start to take (anyone who has insomnia periods will attest)