Simon, The New Testament

The New Testament narrative contains several men with this name, including two of Jesus first disciples. The Simon referred to here was from Samaria, and his story is told in the Book of Acts, Chapter 8. He is sometimes referred to as Simon the Sorcerer.
Simon enjoyed great popularity among the Samaritans for his use of spells and sorcery. The Latter Day Saints would identify his type as using priestcraft - applying religious principles to pursue personal gain. It's hard to know just how this worked on a day to day basis, but he evidently had plenty of paying customers.
The first Christian teaching among these people was by Phillip, who baptized large numbers of people, including Simon. Later, Peter and John came to confer the Holy Ghost on this new converts. Simon witnessed the proceedings, and approached the two Apostles with a proposal. He offered to buy the right to confer the Holy Ghost, much as one magician might make an offer to another to  acquire the equipment or a working knowledge for a dazzling new illusion of some kind.
Given the seriousness of Simon's sin, treating the power of the Gift of the Holy Ghost as a commodity to be traded in the marketplace like fruit or furniture, Peter's rebuke to Simon is fairly mild. Perhaps he realized that mass conversions are something of a hit-and-miss process, and that the level of understanding might vary wildly from one convert to another. Surely, there was error here, but there was no attempt to deceive or set up some kind of competing church. This fellow simply wanted some new moneymaker for his professional bag of tricks.
To be sure, Peter spoke sharply to Simon, but not to the point of expelling him from the church or revoking the baptism he had already received. For his part, Simon did not argue the point or try to justify himself, only asking forgiveness. We don't know what the remainder of his life was like, but we can hope he found a new way to earn a living, and that his repentance was successful.