Possibly My first deal

I got a call that someone want to buy the house from my website. It is not a done deal yet, but I am hopeful and hope that all goes well. I also have another person wanting to buy the house, so hopefully one of them will. I will just be the birddog in this deal, so it is not a big deal, but my first nonetheless. I do have a question though. If the 1st person buys, I will have to tell the second person it is gone. It almost looks like a ghost ad, because it (if it sells) went so fast. So really what is the difference in ghost ads as far as people really know? Houses can move rather fast. Tammy