Mercenary Ninja

A Mercenary ninja (傭兵忍者, Yōhei Ninja) is a skilled ninja who is hired to fight for another country other than their own in exchange for money.
Before the founding of shinobi villages, the majority of the clans in existence at that point were mercenary military forces for hire by whomever. After shinobi are united in villages, however, such mercenary ninjas fight not out of loyalty to their own country, which would classify them all as missing-nin.
Due to mercenaries not being bound to laws of the legal shinobi system, it is a risk to employ their services as they may betray their clients, as Zabuza plotted to kill Gatō once he gets enough money, and Hidari and Ashimaru killing Iori in the midst of a mission for a bigger payoff.
==Known Mercenaries==
* Rain Ōtsutsuki (formerly) 
* Retsu Uchiha
* Zabuza Momochi
* Haku 
* Kusabi 
* Akatsuki 
* Deidara
* Nokizaru Group 
* Sadai 
* Kajūra
* Etoro Konjiki
* Metoro Konjiki
* Hidari
* Ashimaru