In general, if you give a homeless guy $10, he'll spend it immediately. If you give a homeless guy $100, he'll call his friends and spend it immediately.
There's good reason for both these behaviors.
For the first, a bird in the hand is worth two in the bush. You've heard of that experiment with kids and delayed gratification? The ones who don't force themselves to wait for the extra cookie are the ones who got burned in the past. They, and the homeless, know the score. When you can't count on promised payment, you stop taking chances like that.
For the second, of course he's going to spend the money with his friends. His friends were there for him; they helped him in the past. He's got to repay that generosity, otherwise he won't have friends next time trouble comes.