A) Not a job.
B) They have the problem, namely with the person they kill.
Were it to be a profession, they'd be an assassin of some variety, and then those that hire them to kill have the problem with the target's aliveness.
Security guard: that door needs to be watched 24/7 but we don't want to pay for the installation of expensive cameras and an IT guy, so let's hire a security guard to watch the door at just above minimum wage!
B) They have the problem, namely with the person they kill.
Were it to be a profession, they'd be an assassin of some variety, and then those that hire them to kill have the problem with the target's aliveness.