A couple of different forms of corruption can be spotted in Albert of Mainz's career. For one thing, Albert was already the bishop of Brandenburg at the age of 24 and then became the Archbishop of Mainz. Holding a plural title actually goes against the Catholic Church's canon law; however, Pope Leo X agreed to allow him to hold both the bishopric and the archbishopric so long as he made a large donation to build the new St. Peter's Basilica, the church in the Vatican ("History of the Reformation"). On top of the donation for St. Peter's, acquiring an archbishopric is quite expensive itself, and Albert had to take a loan from a banker of 21,000 ducats ("Reformation Day"). In order to finance both his donation for St. Peter's and his loan, Pope Leo X granted Albert permission to sell indulgences, so long as half of the money from the indulgences went to Rome for St. Peter's.
According to Catholic doctrine, salvation comes from Jesus' death on the cross and His resurrection on the third day. Further, a great emphasis is placed upon the accumulation of good works through which you justify your worthiness to accept God's grace. The process of redemption begins at baptism at birth and progresses through good works until the moment of death. Whether or not the believer has accumulated enough grace determines whether or not the believer will go straight to heaven or have to atone for sins in Purgatory, which is essentially a painful transitional phase between heaven and hell. An indulgence was understood as a means of being forgiven the punishment of any sin in Purgatory, so long as a priest had already absolved the believer ("Reformation Day"). The Catholic Church began selling these indulgences as a means of raising money. With the pope's authority, Albert hired Johann Tetzel to oversee the sale of Albert's indulgences. Tetzel particularly corrupted the sale of indulgences by making Catholics believe that the moment an indulgence was purchased, a loved one would immediately be released from Purgatory. He even made up his own little jingle to promote the sale of indulgences: "As soon as the coin in the coffer rings, The soul from Purgatory springs" ("History of the Reformation").
Hence, we see that Albert's career of becoming both bishop and archbishop at once, which broke the Catholic canon law yet was still permitted by the pope, shows us just how mercenary and corrupt the 16th century Catholic Church had become. What's more, Pope Leo X permitted Albert to break the canon law simply as a means of raising money to finance the construction of St. Peter's, and even allowed Albert to sell indulgences to raise so said money, again showing us just how mercenary and corrupt the 16th century Church had become.