How to sell assignment contract

[Ron Feinsod]

I have some investors that want me to find rehabs for them. I know a contract can have a provision for assignment. My questions is how does it work so that the investors do not see the spread between the seller and their purchase price. I don't want to incur the expenses of double closings. If the seller agrees to a price of 50k and I want to make 5k, how do I keep seller and buyer from seeing my profit?