I'm an engineer by degree so a methodological, data driven approach was important to me.  

However, in recent years, I've seen this used as a methodology of raising money to buy low barrier of entry real estate and make sponsors very wealthy collecting fees while leaving the LP's with nothing but capital calls and suspended distributions.

For example, when I google, I often find those types of "Top 10 cities" without knowing where the data is coming from, what the methodology is, and what parameters are they looking at.

Of course not, and neither do we…but they are a part of the business.The methodology we adopt is that our existing tenants are always a little below market rent.  

As for the comp methodology, that sounds pretty straightforward to do.

But they both worked for the same company, were supposed to use the same methodology and certainly had access to their own prior results for the very same property.If we did not need to adjust the total rehab costs, we would have only had the first report.

Investors in the STR market who do not create their own methodology for direct bookings risk getting “killed” in the next economic correction.  

What's the best option with low DP then the traditional 20%.. lastly of you have a awesome lender who is creative and can make it happen, please share contact Info. thanks  Sharing this article I published last year here on BiggerPockets on this exact topic - things are generally the same as when this was written up last Fall - your best bet is likely STR-friendly STR Lenders - ones that will use forward-thinking methodologies like AirDNA, etc. - probably about one third of DSCR lenders are STR friendly at this point (most will not do STR or have very conservative UW)Short-Term Rental Loans: What Are the Options and How Do DSCR Loans Stack Up?

Definitely have learned that methodology. 

I have no problem investors losing money or all of it if they don’t have an approach or methodology.