Hmm...I wonder if Vito had any brothels? When did the Corleones get into da' whores business? Was this part of the move to Vegas ya think?
In both the novel and the movie, it is implied that prostitution in the New York area, was left to the Tattaglias. However, you're right, by the time they got to Nevada, Fredo was running at least 1 brothel for the Corleones. So, my guess would be, after the death of Vito but before or during the move to Nevada.
"I got news for you. If it wasn't for the toilet, there would be no books." --- George Costanza.
