Yet if the numbers were to far exceed the proforma, you can bet they wouldn't be willing to give you any of that money back. :-)I wonder if you could take another actual cabin and do a 5 year example of ownership on the actuals for that cabin and then put that those numbers can't be used as a guarantee for any other cabin's future returns. 

Commercial is your best bet (rates are actually closer to 7-8%) or you can have a loan against your other assets such as brokerage, retire accounts, or a group LOC for your other properties.

Security deposit amountYou can find plenty of examples by searching for "tenant estoppel certificate doc" or exchanging "doc" with "pdf" for more options.Here is an example and explanation: Sample EstoppelSome have a lot of legal jargon but this document does not need to be so detailed.

Might not be 100% safe but it seems like a pretty sure bet

That is a fairly complex exchange that will be difficult to execute.  

That’s the best bet.

The seller has agreed to let us out of the contract but does not agree that we should receive our earnest money back because he says he is able to bet everything damaged and stolen repaired and replaced before closing.   

That being said, I fell out of my chair when I was able to lock an individual investor (personal name) using a 1031 Exchange with about 50% down and 800 credit scores at 6.99%.

I would love to work with someone in the industry that would be willing to provide an educational experience in exchange for sweat equity.

If the parties are willing to forgo title insurance and forgo financing, the exchange of cash for deed and recording of such can be done without third party.