My Uncle is an animal control officer and he has told me that most drug dealers have Pit Bulls and other large dogs as a means of intimidation and protection against other drug dealers and even the cops.
The dogs are also trained to be aggressive towards people to keep them away from the drug dealing residence.
My uncle said that if somebody has more than 4 large dogs especially Pit Bulls and they're not breeding them to sell then they're a pretty sure sign that the people in the house is doing or dealing drugs.
Not always but sometimes.