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). 

Can the store lose it grandfather rights?

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

Hey guys, I was wondering if any of the professional property managers could share with me what online tool do you use to collect payments online from tenants?

I checked it out on Trulia and the location has nice restaurants and grocery stores.

Go to the county clerk of courts online docket and select foreclosure search. 

Can the store lose it grandfather rights?

Sometimes you can find it for free online on a county or cities website.