buying through a wholesaler

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I have a question about buying a property through a wholesaler. 

Is it normal for there to be a nonrefundable deposit (say, $500) in addition to the assignment fee? The deposit is only refundable if there are issues that come up with the title. It does go towards to purchase price but is not refundable like a standard earnest money deposit would be. So if something unexpected is uncovered during due diligence I can't get the deposit back. 

Is this normal or should I negotiate that this fee be waived or changed to a standard earnest money deposit that would be refundable under certain circumstances?