"Street" selling is the bottom of the chain and can be accomplished through purchasing from prostitutes, through cloaked retail stores or refuse houses for users in the act located in red-light districts which often also deal in paraphernalia, dealers marketing merriment at night clubs and other events, or directly from dealers who have purposefully engaged adolescents (typically). Many users sell in order to fund their own drug use. Although most are in it for the monetary outcome, some view narcotics dispensing and consumption as a means of insurrection and orchestrate it for that cacoethes. They refrain from intensive processing and abstain from umpteen 'business' practices. Although most dealers market to a changeless customer base, these mavericks may be overly advertised on hacker/phreaker/drug/etc. forums and between friends and cohorts.
U.S. Government guide to spending on illegal drugs (http://www.whitehousedrugpolicy.gov/publications/drugfact/american_users_spend/)
U.S. DOJ history of illegal drug trade (http://www.usdoj.gov/dea/deamuseum/museum_illegaldrugs.html) (rather self-serving and biased, represents DEA as triumphant over drugs)
Drug and alcohol addiction is a universal problem, and now, in the 21st century, with the help of the numerous research and studies conducted, there are several ways to fight this and come out of the spell of substance abuse addiction.
Many people who are active in their addictions find it very difficult to accept that they are actually abusing a substance, and in many cases, they are in permanent denial.
Drug addicts sometimes feel that they have adopted a different way of living, and even if there is danger to health and life because of their abuse, they think that they are in control.
Drug dealers are stereotypically associated with organized crime syndicates, though they often work freelance in reality and bear no connection to organized criminal groups.
The trade of these hard drugs is driven mainly by the economics of greed and often by poverty, and in many cases by addiction, though there are some exceptions to this.
The main organized drug cartels deal with cocaine, heroin, and MDMA, and it is these that are the primary focus of the United States Drug Enforcement Administration.