@John Horner I have run into this before and will run into it again, but it's not the end of the world. I will usually call my buyers who I am 90% will end up taking the deal, run the scenario by them with pictures/video and make sure they are confident they want it. Then I will schedule a time to walk them through the house while the owner is present.
If I get to a point where I am marketing a property to buyers who are not on my A-List nd I am not sure how serious of a cash buyer they are I have had them sign and assignment contract with deposit and I will give them a 24 hour clause to back out of the contract after the inspection. This helps me gauge how serious the buyer is before I show them the house. Odds are I'm only going to get a couple chance to show the house before the home owner starts getting curious/irritated because they obviously don't want the process to feel as if they have their house lsited on MLS with potential buyers in and out all the time.
You can easily wholesale this property before closing, it just takes a lot more due diligence with your buyers throughout the process.