I think all of these are easily trumped by the ol' bit of common sense : "a bird in the hand is worth two in the bush". Don't trust someone who is a professiona

I think all of these are easily trumped by the ol' bit of common sense : "a bird in the hand is worth two in the bush". Don't trust someone who is a professional crook to propose you a deal that includes long term promises. If people want to pay half later, find a way to cut what they want to buy in half and give it to them at this time and make no promises yourself either.