There's no escaping the fact that Airbnb is an enormous marketing engine that will drive the majority of your business.

This made me an enormous cashflow since there was initially nor mortgage (about 900/month).

Given the long term nature of our relationship with the owner, he was kind enough to allow us to view the listing before it went public and given we had already completed an enormous amount of research into the project we were able to offer full asking price.

Given the long term nature of our relationship with the owner, he was kind enough to allow us to view the listing before it went public and given we had already completed an enormous amount of research into the project we were able to offer full asking price.

The potential tax savings I'm calculating after solo 401k deductions appears to be enormous versus not opening the business at all and I can't help but wonder if I am missing something?

Plus, the election may well have an enormous impact on real estate prices.

What you read was  most-likely written by someone full of b.s..While there are sometimes some 'lease-option' deals there are probably more of those deals that went bad than were successful.There is a enormous number of things that go wrong with lease-option deals because even though you have a written and signed contract the contract is not worth the paper it is written on when the seller decides he (or she) no longer wants to sell you the property. 

I'm assuming the current owner has no debt (100% equity), which would man that 7% would be an enormous profit.Also, if this is 100% equity, this isn't a loan you are getting, which means the seller retains title until the entire amount is paid off.This sounds like the seller has you by your lower tonsils.  

It's not hard like rocket science, brain surgery, or other things that require an enormous intellect in addition to the hard work. 

It is usually through the practice of rent shifting:  They have enormous booking fees, which they do not share with you, and offset them by lowering your rent.