the sale of indulgences was a fairly common practice during the middle-ages, before the protestant reformation, though not an entirely legal one. for a price, people, usually well-to-do catholic ones, could guarantee entrance to heaven (i.e., salvation) to themselves and as many friends and relations as they could afford.
anyone caught selling indulgences would be excommunicated on the spot, which was considered a far more serious punishment then than it is now (it's such a joke now, in fact, i don't even think they bother doing it anymore...excommunicating, i mean) but even still, the income these con-men raked in made it well worth the risk.
individuals have long since quit peddling salvation. now the church itself does it, has a monopoly on it, so to speak, and sells it in the form of declared masses. now do you see where i'm going with this?