One of the biggest moneymakers for the Mafia families has been through loansharking, and in February 1965 the FBI's New York Field Office prepared an 87-page report for Director J. Edgar Hoover on so-called shylocking which details the racket and identifies its players.
According to Joe Valachi, the Genovese soldier who became a national hero by ratting out his paesani, shylocking was among the mob’s top three rackets with gambling and drugs as the other two. The FBI report states:
Joseph Valachi advised on October 29, 1962, that the most lucrative money makers of those in "Cosa Nostra," to his best knowledge, were narcotics trafficking, gambling and shylocking. He stated that of these three, in view of the tremendous adverse public opinion and sentences, narcotics is reduced to the lowest money maker of the three. Valachi stated that gambling and shylocking are about equal as money sources for members of "Cosa Nostra," but that shylocking is the easier of the two.
Shylocking was about more than usurious loans to degenerate gamblers who got their legs busted after missing payments. Many operations were sophisticated ventures set up as corporations or partnerships which differed little from legitimate lenders, and they provided loans to small businesses and homeowners in exchange for security interests in their property. These loans were profitable in their own right but also provided the Mafia a vehicle through which to launder its dirty money -- often from the drug trade and other illicit activities -- and the means to acquire legitimate businesses if the borrower defaulted.
The FBI report provides "a list of prominent shylocks" which "is by no means complete, inasmuch as virtually every member of 'La Cosa Nostra' at one time or another engages in shylocking." The FBI list identifies several dozen supposed shylocks and describes their alleged activities, and among them is John "Sonny" Franzese, the currently imprisoned Colombo underboss, who in 1965 according to multiple sources was "the fastest growing and most prominent shylock in the Greater New York area" and "engaged in taking over New York night clubs through his shylocking enterprise."
This report is among the FBI files relied upon in The Mafia and the Gays by Phillip Crawford Jr. -- available at Amazon either as a Kindle e-book or a trade paperback -- which provides a comprehensive look at the mob's involvement with gay bars from the post-war years through the mid-1980s.