The Collaborative International Dictionary of English v.0.48:

Hireling \Hire"ling\ (h[imac]r"l[i^]ng), n. [AS. h[=y]reling.
   See Hire, n., and -ling.]
   One who is hired, or who serves for wages; esp., one whose
   motive and interest in serving another are wholly gainful; a
   mercenary. "Lewd hirelings." --Milton.
   [1913 Webster]

The Collaborative International Dictionary of English v.0.48:

Hireling \Hire"ling\, a.
   Serving for hire or wages; venal; mercenary. "Hireling
   mourners." --Dryden.
   [1913 Webster] Hire purchase agreement
   Hire purchase

Easton's 1897 Bible Dictionary:

Hireling
a labourer employed on hire for a limited time (Job 7:1; 14:6;
Mark 1:20). His wages were paid as soon as his work was over
(Lev. 19:13). In the time of our Lord a day's wage was a "penny"
(q.v.) i.e., a Roman denarius (Matt. 20:1-14).

Moby Thesaurus II by Grady Ward, 1.0:

25 Moby Thesaurus words for "hireling":
   adventurer, assistant, condottiere, drudge, employee, free lance,
   girl Friday, grub, grubber, gun, gunman, hack, hired gun,
   hired hand, hired killer, hired man, man Friday, mercenary,
   myrmidon, pensioner, professional killer, right-hand man, slavey,
   soldier of fortune, worker