Indicators of a drug house would be high levels of pedestrian and/or vehicle traffic at all hours of the day and night, exchanges between people that appear to be drugs and/or money, and people appearing to be lookouts around homes or buildings.
These indicators alone may not mean that drug dealing is occurring. However, some of them happening together may indicate a problem.
Customers of drug houses often generate money through criminal activity other than drug dealing, such as burglary, theft, robbery, identity theft, and prostitution. Often times the customers will commit these crimes to generate money to pay for their drug habit. This can also have a negative impact on the neighborhood.