Due Diligence period on NC Contract and Non refundable EMD

I needed clarification in a real estate purchase and sale agreement on a wholesale Offer to purchase agreement.  1) The correct way to explain to the seller whether this is negotiable or not 2) if negotiable who negotiates it  ( buyers agent /seller agent in case the best use case is wholesale ( realtor to represent the wholesaler) What is the true logic behind the non-refundable due diligence, in wholesale transactions if the wholesaler is not taking title to the property how is it reflected in the contract, does it get subtracted from the purchase price or not?