Help! Can you use an IEE contract to do a morgage assumption?

Hi all!

Please help if you know the answer. Am I able to use an
IEE contract to do a mortgage assumption (instead of an outright buyer getting a loan right away)and just get paid a year or so later at the close?

Scenario :
Found seller who is willing to have someone just take over their existing mortgage, then to have the buyer refinance and buy within the next 1-2 years. Can I write a 'subject to existing financing' contract for the new buyer and seller and receive my fee a year or so from now at closing then?

In this scenario, would the 45-60 day lock up need to be changed to 1-2 years? I would think not if the new buyer is signing the new contract within the 45 to 60 days I have the prop locked up on contract.

In this scenario, could the end buyer get FHA financing? I wonder because you can not 'assign' to an FHA buyer, unless they pay your 'fee' separate from the FHA loan they receive (FHA will not pay the fee). So I am wondering what an FHA lender will say to in regards to the paper that has my 'fee' on it at closing??

Thanks!
DC