someone who does a job purely for money, rather than out of interest in the work itself
it may be truly affirmed that no kind of men love business for itself but those that are learned; for other persons love it for profit, as a hireling that loves the work for the wages;.
disapproval If you refer to someone as a hireling, you disapprove of them because they do not care who they work for and they are willing to do illegal or immoral things as long as they are paid. someone who will work for anyone who will pay them - used to show disapproval