If it's Wednesday and the first person says, "I can come by Friday and look at it." and the second person says, "I'll be by this afternoon.", I'm not going to tell him, "No, you have to come by after Friday."You shouldn't be setting up an earlier time with someone, you've already got your buyer lined up.
Cash in hand.
Maybe that makes me a dirtbag in your eyes, but I've known enough salesmen to know that 90% of salesmanship is being okay with people calling you a dirtbag. As a buyer, I always make the appointment as soon as I can, because if it's a deal someone else might beat me to it. If they do, I don't complain.