So I am having a new experience this week. I am trying to sell my car!!

I've never had to do this before....my first car was totaled in a hit & run accident...my second car was sold to a friend for $500. This time I am having the WHOLE car selling experience...placing the ad, fielding calls, showing the car, lowering the price, etc. As of yesterday things were looking really good. Appeared to have a buyer. Said he would call me today, and would have the money to me today or Tuesday. As of tonight, I haven't heard from him. I've called twice, and in my book three times in one day is stalking!

I do have two other potential buyers, but neither has come to see the car because I thought it was a done deal So, now I don't know what to do.
How long do I give the guy to get back to me before I move on?? Ahhhh drama! Any advice? Thanks.