Preferred returns would even be acceptable but not a straight interest rate play if the lender understands the structure. 

The automating of reviews I understand.

A good way to get an understanding of how to get into STR is :STRATEGY: Start Up Guide to Short Term Rental Investing 

Did you speak with them prior to purchase to understand their process?

This is actually quite helpful insight in understanding the reasoning. 

Verifying last 2 years of rental history and income extremely important to find the “best of the worst”.Make sure you understand the Class of properties you are looking at and the corresponding results to expect.The City of Detroit has 183 Neighborhoods we’ve analyzed.DM us if you’d like to discuss this logical approach in greater detail!

Why do you want to work with agents who don't understand simple things like owner financing in real estate, it's really simple.

What or who do you suggest I speak to or learn from to better understand my options for mortgages?

I understand if a contractor doesn't want to agree to it.

From what i understand, the space heaters are a big fire hazzard. does your insurance allow them?