As I've mentioned in other threads, we had a couple of drug wholesalers operating out of my old neighborhood. They sold to the street dealers.
It took well over a year for the police to get a warrant. Once they did, they found every cupboard and closet filled with cash.
The two punks who ran the place probably could have gotten away with it for a long time, but they were too high-profile with their Jaguars and Cadillacs, and their attitudes. If they hadn't been so flashy and obvious, the neighbors wouldn't have noticed, and without the pressure from and cooperation of the neighbors, the police wouldn't have been able to get a warrant.