Are you going to just photograph homeless people, or actually going to do something positive to help their circumstance? Payment perhaps?
I was homeless myself in the 1980s. There are friendships that are formed and interdependencies and bonds built over time. If somebody leaves or dies, it affects the whole group. I am not aware of photographers in Melbourne, here in Victoria, actively seeking out homeless people in their known places, especially since recently a homeless man was murdered in a thrill kill by a teenager. To me, it is morally corrupt to photograph homeless people either as documentary or presumed interest in the finished image — it's a difficult, cold, lonely and risky life of nobody's own particular choice in many cases. So if you are going to photograph people form a friendship and provide a small token of sustenance to see them through another night. It makes the world of difference.