Smiles.

"A smile is the universal welcome."
~Max Eastman
They say "A picture is worth a thousand words," and I agree with that. If there was a picture of something magnificent, it'll have a thousand of great words describing it. If there was a picture of something horrible, it'll have a thousand words of discouraging words describing it.

To me, a think one's smile is worth more than a picture.
When you see one's smile, you'll know that the one is happy. Does it make you happy to see another one happy? Well your answer should be "yes."
Honestly, me seeing someone else smile is even greater than my owns. I see that they are delighted with life at that point. We should have more of those moments.
When you see someone frowning, you should always be a caring person no matter who this person is. If it takes you to make a homeless person happy, do it. It'll make you happy as well; since you had done a right thing.
So next time you see a homeless or anybody at that, the least you can do is smile.