The reason is you want to know the value of the business you are buying, so that you can compare to other investment opportunities. 

Interesting but I don't have a lot of money that is why I'm willing to sacrifice time/sweat in rehab for a low budget property that after its done is like 40% cap rate compared to 12-15% on a single family normal rehab property.

If I compare the Schiller SFBayArea median home price vs S&P500/NASDAQ, the percentage increase since 2000 seems to be about the same.

I use a rewards credit card and pay the balance off every two weeks. 

They also use my brokers' license allowing us access to the MLS for retail selling of property and comparable information.

I don’t know about the specific property you are talking about, but my guess would be someone is using a HUD financing product that comes with a restriction that they have to rent to people below a certain standard compared to the median in their market.

They expect a smart borrower to shop around and compare terms, ask one lender if they'll match or beat another.

Initially my wife was pushing for the heloc as the method to get our down payment money but I insisted on as closely as possible comparing the numbers to the cash out refi. 

Sometimes failure is just the tuition in the education of investing, most times far more rewarding and educational than success. 

Those are good places to start but you should always look for sales that are comparable in type, size, condition, and amenities.