Find a Need and Fill It

On my recent trip to New York City, the heart of consumerism, aside from going to the regular old places like Times Square and Central Park, we decided to take a walk across the Brooklyn Bridge. It happened to be a hot day and when we started walking, a few times throughout our walk we saw people selling bottles of water for $1 in big coolers of ice. It sounds simple but there's a strong message. They found a need and filled it, and sure enough, a lot of people were buying. Now, if you had one cooler of ice to put anywhere on the bridge, where would you put it? At the beginning? In the middle? Or at the end?