Be careful not to mistake "real users" with paying customers. If your aim is to build a business, then making that distinction early on is crucial. As far as your first sale is concerned, ask yourself who is your target customer, where are they, what do they do, and how do they do it. Then, simply walk up to them and tell them that you understand that they have an urgent problem which requires an immediate solution. And that you are able to provide that solution to them today at a price that they will find agreeable. Good luck!