Final answer:
The practice of purchasing church offices for inheritances is simony. The sale of indulgences, protested by Martin Luther, was an entirely different practice involving payments to reduce time in purgatory.
Step-by-step explanation:
The practice involved in the purchase of a job by the wealthy for ineligible sons to gain an inheritance is known as simony. Simony is the act of buying and selling church offices and roles, which was strongly condemned by the Church, especially after the Cluniac movement's influence. However, the sale of indulgences, which was a separate practice, involved paying money to receive a piece of paper asserting that the payer's soul would spend less time in purgatory, thereby reducing the atonement period after death before entering heaven. Martin Luther famously protested against the sale of indulgences in his Ninety-five Theses.