Found in all corners of the galaxy, the typical mercenary is a former military or police officer who completed his term of service and is marketing his skills for a much higher wage. But even at the best of times, there is little quality control or accountability in the system, and frauds and unprofessional thugs are a constant problem. To counteract this, the largest private military contractors offer their own training and certification courses, to the point where would-be mercenaries can join the company with no previous experience and come out with all the necessary skills.
Mercenaries work for a wide variety of employers. Governments top the list, overwhelmingly preferred by most companies for their deep pockets, long terms of employment, and appearance of legitimacy. However, mercenaries are also found working for rebellions, colonist collectives, corporations operating in war zones, or illegal but well-funded interests such as pirates and drug cartels.
It is for this reason that most nation-states or galactic governments frown on the use of mercenaries, at least by their opponents. The Citadel Conventions reflect this disapproval, stating that mercenaries captured in wartime are not legitimate prisoners of war, but criminals on the battlefield, and they may be executed without violating the laws of war. While some mercenary groups are lobbying to change the articles of the Conventions, most see the associated risk as a unique badge of courage.