A hired gun. Yeah because those are so common. Everywhere are hitmen out there and its similar to booking a hooker, also they kill people daily....
Word of Mouth jup thats how they get new jobs.
Not going to pretend I know all of the world but I bet no proffessional Killer wants to get known through word of mouth. If you get an idiot to do it fine but he wont run free for long. Also have you ever heard of a proffesional Killer that does this "Job" privatly and kills on a regular basis without beeing caught for a significant amount of time ? A Hitman doesnt look for clients. They bite if a opportunity presents itself and dont kill every week month or even year because thats stupid.
People who think they can just hire a killer through a friend, craigslist or the silkroad are stupid. And its pretty dangerous to do that because if someone really does it he will rip you of and not wait for your 5 star rating on his homepage and wait for your neighbours to order a hit.