The important factor to all this simply is; communication is not hard to do effectively. I have not had a problem in any of my dealings, perhaps I over communicate.. lol. But, if i am the buyer I always advise of a payment date. And if I am a seller I always ask for the payment date. Things can happen to change these, but one quick message makes it not even a problem. Just communicate and you and your buyers/sellers will be happy and eager to do further trades. I have received ridiculous offers in the past, but still reply even if it's with " haha, are you kidding?!"