Regarding the question of whether homelessness is a personal choice: from my observations, it does seem to sometimes be the case. For a variety of reasons, some people just can't handle living in a shelter, or in an house or apartment - so, some of them choose to live on the streets, even though they may be miserable at times. That's just the way they are. A lot of times, that's due to mental illness.
As communities, it's up to us to deal with that reality. We're always going to have some people who are going to live on the streets. They're citizens, too - and they have all the rights that the rest of us have. In most nations, that means that they are entitled to a significant amount of personal freedom and dignity.
-Joe-