A member of the Englewood (Florida) Camera Club introduced me to the work of Chuck Ferris, M.D. He is a psychiatrist practicing in San Francisco who has an ambitious project of interviewing, and photographing, the homeless. His website is HERE.
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The site has several galleries of still images. Also, there are collections of video interviews with homeless people that are very insightful. A page containing six separate interviews can be seen HERE.
Having met and photographed a number of homeless people, I can say that they have been uniformly open, and easy to talk to. I hope that you check the work of Chuck Ferris, it is quite unique.