Many states land records are on line.

While searching the internet for weeks and contacting a lot of brokers, I have had a very hard time finding any broker versed on this niche and able to help. 

An internet stranger brought up the very good point that there's literally no reason NOT to have as much HELOC open as possible since the payment on $0 drawn is $0, and there's a lot of family emergencies that can be solved by clicking my mouse 10 times and dumping $50k into my checking account. 

Moving to Quickbooks Online and producing a balance sheet and P&L helped a lot, it then looks like any other business.My new guy looked at the cash flow as not contributing to retirement income until the mortgages are paid off (my net with mortgages is trivial).

Go online and verify the bills.

We got a bunch that was discounted online to $0.61/sqft delivered Freight to a property. 

From what you describe, assuming that existing rental income is honestly reported on your tax returns, you should be able to count both rental income from the existing property, and projected rental income from the other units in what you are buying, assuming a local REI-friendly lender with minimal/no overlays (those are the reason why you see conflicting stuff online). 

You can also check their reviews online at Google, Facebook, or Yelp.

These days, you can check Zillow and find out how long it's been on the market, so if it's on the market for over 90 days, they're asking too much.As to real estate taxes, figures are available on online, and can go up on changeover of ownership.

@Kelvin Tian here is a calculator that has an amortization schedule and what happens when extra payment goes to principle. www.free-online-calculator-use.com/extra-payment-mortgage-calculator.html