At first, I had lots of free users who came from the wait list I had set up. Each new user got 200 free "credits" – the fuel that the AI is running on. Each article that the AI finds and ranks for relevance (inside an online forum where people talk about the problems you solve), this article consumes one credit.
So most of the users consume those 200 free credits and stop.
The first paying customer was one who had already bought 2Quiet2Market.com, another product of mine, so they knew that I make good stuff. But then, other customers bought credit packages as well, and that was really encouraging.