I think you're going to have to resign yourself to the loss.FB Marketplace is a cess pool; you're not going to get any serious buyers there, certainly not ones that wouldn't expect some hefty discount.

Buy a note with a interest rate similar to the seller financed note at a large discount due to the relatively low interest rate and long term - and “substitute” this note for the seller financed note.

Even gave me a big discount.

I've got a deep discount on a truly passive STR.I've got a lead on a deal that can be purchased almost $100k under list price given the circumstances.

Discount manager = discount services. 

They then informed me that I could either move forward with the management services, with a nominal discount of $110 for the error, or revert to the Lease Only Option and have the lease transferred to me without any security deposit, as none was collected by the property manager.This mistake has left me in a difficult position.

I purchase the home at a substantial discount.

This can get to 100% end financing in more expensive markets with smaller ARV discounts....though positive cashflow is a separate issue that must be overcome :)   Question: Is there anything in Freddie/Fannie rules that would prevent me from the scenario below?

It's like working for free or at a discount and hope that you make money.

First month payment came through, PM had discounted first rent 50% off without passing it by me.