I don't know. If he deserves to die, sure. If not, no.
It depends on the person. If you asked me to kill someone I hate, such as a child molester, murderer, dictator, and so on, I would be happy to do it for free. If you asked me to kill someone I'm neutral on, such as person B in country C, I would NOT do it. If you ask me to kill someone I love, I would NOT do it.
I would not ask money for it, but if they give I would probably donate it to a charity or something.
I've never taken someone's life before, but I did once came dangerously close. My brother and I was attacked by one man with a knife. He tried to stab us but we (read: my brother) kicked him unconscious and left him. If I had my .38 on me I would have shot him and left him there. (This is in South Africa btw)