In makes a certain amount of sense (from an evil perspective) that the devil would allow humans to earn money off unrighteousness (see Revelation 18:9 - 19), since this would be the opposite of what God would allow. Jesus' response was swift when he found those taking advantage of people entering Jerusalem's temple.
14. And He (Jesus) found in the temple (the outer court of the temple) those who were selling oxen and sheep and doves, and the money exchangers sitting there; 15. And after making a scourge of cords, He drove them all out of the temple, with both the sheep and the oxen; and He poured out the coins of the money exchangers . . . He said, "Take these things out of here! Do not make My Father's house a house of merchandise." (John 2:14 - 16, HBFV throughout)
In the New Testament, a person named Simon (Simon the Magician) made quite a bit of money practicing sorcery. The signs and wonders he produced almost certainly were demonically influenced, as they mesmerized the ENTIRE city of Samaria from the youngest to the oldest. The people of the city were so impressed that they erroneously attributed his power as coming from God!
9. But there was a certain man named Simon, who had from earlier times been practicing sorcery in the city and astounding the nation of Samaria, proclaiming himself to be some great one. 10. To him they had all given heed, from the least to the greatest, saying, "THIS MAN IS THE GREAT POWER OF GOD" (Acts 8:9 - 10).
Another classic Biblical example of using evil spirits to make money involves a slave. In Philippi, a slave girl who was possessed of a demon (literally "a spirit of Pythoness" or one of the demons who guarded Delphi), made huge sums of gold and silver for those who owned her.
16. Now it came to pass that as we (Apostle Paul, Silas, Timothy, Luke and possibly others) were going to prayer, a certain damsel who had a spirit of Python met us; and she brought her masters much gain (money) by divining. (Acts 16:16)
Her power of divination, however, was lost when Paul cast the demon out of her. The owners of the woman were so mad at the loss of their income that they had Paul and Silas brought before a local court, beaten, and put in prison (Acts 16:17 - 24)!
Another person who practiced sorcery for a living was named Bar-Jesus. He ingratiated himself with Sergius, the Roman-appointed ruler of the island of Cyprus. When Bar-Jesus resisted attempts by the Apostle Paul to preach the gospel to Sergius, Paul called him a "child of the devil" and caused him to go blind (Acts 13:6 - 11).
While throughout history there have been those who are either influenced or possessed by evil spirits who make money from the relationship, still others simply PRETEND to have tapped into the powers of the spirit world in order to make a dollar.
The seven unconverted sons of a Jewish priest named Sceva were traveling exorcists who made money telling fortunes and pretending to perform exorcisms and healings (Acts 19:13). These men neither had authority from God to cast out demons nor were empowered by evil spirits (see verse 15 below plus see Matthew 12:24 - 29).
One day, while in the area of Ephesus, they attempted to cast a REAL demon out of a man. The consequences of trying to make money through pretending to have power finally caught up with them.
14. Now there were certain men, seven sons of a Jew named Sceva, a high priest, who were doing this. 15. But the wicked spirit answered and said, "Jesus I know, and Paul I have knowledge of; BUT YOU, WHO ARE YOU?" 16. And the man in whom was the wicked spirit attacked them, overpowered them and prevailed against them, so that they escaped out of that house naked and wounded (Acts 19:14 - 15)
Money for nothing
In modern times, there are those who are paid money feigning they can talk to the dead, or who pretend to foretell the future through tarot cards, reading palms, fortune-telling, horoscopes and so on.
A good example of pretending to have a special or unique supernatural ability can be found in a U.S. cable television show called "Long Island Medium." The show centers on a woman who claims she can contact the spirits of those who have died. James Randi, known for his skepticism regarding those who claim supernatural powers, wrote an interesting article regarding the show. His comments highlight why making money from such endeavors is anything but harmless.
"TV psychics do not talk to the dead (nor do the dead talk back to them!). Mediums cannot show they do anything more than cold reading [the technique of picking up personal info through conversing with a person then using it to pretend to know specifics about them] nor that what the TV audience sees is just selectively edited to show 'hits' and ignore the 'misses.'
"But much more importantly to us, such performances seem to prey on people at their most vulnerable moments - those who have suffered the loss of loved ones - and these mediums use such grief to make a buck. Psychologists tell us this keeps the grieving stuck in their grief, rather than going through the natural stages of acceptance that are healthy" (article "The 'Medium' Is Not the Messenger" published in Wired Magazine).