Hello Brandon i'm still new to wholesaling myself i'm currently in the process of closing my first deal. But here are some helpful tips that I think you can use and will answer your question:
1. I never let a seller know that I will be assigning the contract to the property so the conversation is never even brought up. I always tell them that either I will buy there property or one of my partners will ( I always refer to my end buyers as partners) but either way they will receive the agreed upon amount for there property. ( Sellers don't care who buys there property they just want it sold).
2. In the Purchase and Sale Agreement I have in the contract that the PSA could be assigned and that the seller is not entitled to the assignment fee.
3. Don't use an actual " Assignment of Contract". You want to use two purchase agreements, One between you and the seller, and one between you and your end buyer. This way you are never discussing assignment fees and only discussing the purchase price. If you work with an investor friendly title company they will know that the differences in the two contracts is your assignment fee. You can also ask them if they will leave your assignment fee off of the HUD statement.
Hopes this helps.