Help with paying a finder's fee.

[Eugene Koh]

I am going to ask people to find me houses that I can wholesale. I will reward them 250~500 AFTER closing but how do I assure them that I am not scamming them? What can I do to them to make them trust me that I'll give them 500 after I close. Won't they think that I might start ignoring them and run off with the distressed property so I don't have to pay them?