First, don't shoot homeless people. It's cheap and hardly ever makes for good street photography.
Second, a small camera with a single lens is crucial. Obviously most street shooters use a rangefinder for this reason.
Third, no telephotos. This will only cause you grief. The lens is big and intimidating. People think you're stalking them because you're pointing a giant lens in their direction from across the street. It makes people uncomfortable.
Third, make yourself invisible. This means small movements that are deliberate. Running around snapping at everything draws attention. Don't fiddle too much with your gear.
And last, be humble and empathetic. Smile when someone notices you've taken their photo. Don't try to hide the fact or turn around in shame. Make eye contact, give small smile as to say "it's all OK, thank you for sharing a moment of your life with me that I'll keep as a photograph" and then move on to your next subject. I've never had anyone get in my face screaming and yelling. Occassionally, I'll get a head nod or a smile in return.