Wholesaling: separating the real from pretend end buyers

[Nicholas Hooyman]

I recently read Nasar Elarabi's article about mistakes to avoid when you're a newbie wholesaler.  Well, I'm a newbie wholesaler, so this is of particular intrigue to me.  My question is about something he said in his article:

"...be careful of separating the real from the pretend buyers by simply asking for a non-refundable earnest money deposit from your buyer."

Specifically, I'm wondering this works... pragmatically.  Let's say I have a purchase and sale contract already signed.  I find an end buyer who I want to assign that contrac to.  Do I set up escrow and give the title company the contract and the end buyer delivers the non-refundable security deposit to the title company?  Then I get that deposit when I deliver the contract?  Is the amount of the deposit my entire spread in the deal or is it just a portion of my spread and I get the rest when the deal closes?  

Any help would be much appreciated.  Thank you for your time.