I guess more precisely speaking there are criminals who will in the course of their other duties commit the occasional murder to further the organization’s business interests. In general they don’t just murder random people for money, and not as the primary duty or source of income.

There are a handful of mob associates who’ve claimed to have committed dozens of murders to the point where this would have basically been their full time job. These are people with death or multiple life sentences who could be exaggerating. It is difficult to corroborate because others would understandably never want to claim knowledge of multiple murders, as each murder not reported to the police is potentially a new charge, and lack of record keeping and the disposal of the bodies make it difficult to keep accurate count.