Structure deal on new construction spec home with construction financing

[Antonio Pican]

Hello,

We are being approached to GC/partner on a spec home with whom the client owns the lot and will be securing the construction financing himself in order to do the deal. We will be drafting up a contract for the lender with X amount cost to build/finance. Once the home is done we will be selling it off and splitting the net profit.  My question is since a lender is involved and I will be drafting up a contract how do I protect myself as to once I hand off the home he doesn't end up pushing me out (there is no sign of such and there is trust but this business)? Do I draft the contract price for higher than the actual build price that would include our estimated profit (sell price) or would a separate agreement between the lot owner be sufficient enough that outlines the deal since we don't know the actual sell price until it goes to market? Trying to keep this as clean as possible. 

Thanks in advance.