Shops? That would just be...odd. I mean, you are walking around "evil" territory, right? If there just happened to be some surviving human who also happened to be a shop owner, do you really think, during these dire times, he would require you to buy goods from him with money? It just seems very odd...
Perhaps you collect money throughout the game and, depeneding on the amount you have by the end, you recieve a different ending? You have the "rich" ending and the "poor" ending or something.