When Geary meets with Michael in his office during Anthony's party, he says "You [Michael] own or control three hotels--two in Vegas, one in Reno....now you're planning a move on the Tropigala" [he doesn't say where that hotel was]..

But, to your broader point, the movie never identifies any other businesses or rackets Michael might have had in Nevada, other than Fredo's brothel. This is a bit of a mystery: On the one hand, it would have been dangerous to Michael's "legitimate" front to have button men and rackets all over Nevada, or California, or elsewhere in the West, and it could have resulted in the Gaming Commission investigating him and yanking his licenses. On the other hand, he appears to have been a billionaire by the time of GF III, and I can't believe he made all that money from just four casinos.