Vice make the awesome documentaries which nobody else dares to. In this 20 minute long 2012 feature How To Sell Drugs (once also titled The Secrets of a Drug Dealer) the producer follows a New York man who claims to sell $100,000 worth of drugs per week. He gives the viewer a unique insight into the inner-workings of his operation, even telling the viewer how his workers operate and how he sources his product. The dealer claims to be able to supply literally any illegal drug that you desire.
Interestingly the dealer featured in this film was arrested just a few weeks after shooting but released the day after, he claims that he participated in the film because he was aiming to get out of the game within a few months of filming. Names and places are disguised in the film for obvious reasons.