A hireling is someone doing a job solely for the money. Hirelings have a bad rap because they don’t do anything out of the goodness of their hearts; they work only for cold hard cash.
If you have been raised with the idea that there is dignity in hard work of any kind, it may be hard to understand the negative connotations associated with the word hireling. A hireling isn’t just someone who’s hired to flip burgers, a hireling is more like a mercenary, which is a soldier who fights for whoever’s paying. Hirelings often do jobs that are distasteful, ones that could involve lying, cheating, or worse.