The killing of Willie Moretti in NJ in the 50s was an open contract according to the Valachi Papers. He was in the Genovese Family, but killed by an Anastasia family guy. There is another story which I can't find confirmation of anywhere, where Vito Genovese said some associates who shot at a made guy should be killed "on the spot" if anyone saw them.
I don't think they pay for hits. None of the rats have said anybody paid them for doing "work". And if you did carry out a contract,how would you collect? What would you do if they didn't pay?