This is in Maryland in case that matters.Thanks How would you even determine the interest rate? 

That would determine market rents for your type of property and value it that way.

Credit scores are often determined by how many accounts you have open and how long they’ve been in effect.

Generally, I am looking at the numbers to determine cashflow.  

My advice to anyone investing is to first determine what kind of REI property you are looking for, talk to the locals, get on automated searches, tour or have a real estate expert tour for you interesting properties, get your financing in order and get ready to "Pounce" once you see a property you want as it's still a Seller's market and many are vying for the same property as you.

Trying to determine the best way to negotiate the property because I believe he still has a mortgage on it I don't see a discharge of the mortgage in the records, but that also brings up a question for me as to how can I offer a lower amount of the property than what he owes on it.

To be clear; the valuation comps the county is Required to use are sales that occurred in the last quarter of 2017, when values are determined for 2018.  

I am truly determined to become an investor.

@Gregorio Martinez a municipal agency like the county accessor has no way to accurately determine actual value.

you got scammed its rampant on the internet..