I am not a businessman, but I always have some cards in my messenger bag. I print them on my own with a color laser printer and cut them out of the sheets with a scissor. I put my name, my website at 500px and my email on it.
big visual business ;-)
Out in den streets I also take some portraits and you save some time if you have your card ready after the photo is taken. That will also put some serious trust into the whole thing. I always tell people that they will find their photo on 500px and that they can send me an email if the want the photo in original size for their own. And maybe you meet another photographer and want to exchange contacts on the go.
dance - X100 @ f2
And don´t forget to tell them that they don´t have to pay for the photo and what street photography is all about (the short story). Because street photography is a kind of a life style and you do a great job when you tell people more about this form of art.