Exclusive marketing rights to raw land property?

[Kyle Conrad]

Curious as to whether anyone's ever signed an exclusive marketing contract with a potential buyer. Essentially, I'd like to pay the seller a fee for granting me the right to marketing his property. I'd pay him $500, market his land to my buyer's list, and take care of the transaction and closing costs once it sells, possibly giving him a portion of the profit. 

This would be for a piece of raw land that has a couple of 'question marks', e.g., an adjoining landowner has built a fence through it, it can only be accessed via a private drive. It does have value and I do think it will sell (eventually.)  

Obviously, the point of this would be to mitigate my own risk so I wouldn't have to invest my own cash to purchase the property. Has anyone ever heard of this type of agreement?