The listing should be on the local MLS You can always check the "data source" noted on realtor.com to see what MLS' are used in a given area. b.

Often times you are only seeing a "view" or "report" of the information available on a listings, not every single data item available.

What do you hope it will achieve for you? 

Spend time on this and not on property management and you’ll achieve your goal.

Get into the data of how our cities are changing and growing.

Where is a good place to research local demographic data for target locations, such as income growth, job growth, population growth, median rents and median income, as well as other important info? 

Of course, if you are planning to sell that may complicate whatever you are trying to achieve.

My instinct is telling me I'm doing things wrong: that third party sites offer neither unique data, nor fresh data, and that I'm wasting my time browsing them.

There are different places you can run data to be able to get a better idea if this will work, but the property needs to be nice and also in a good area at the end of the day.

  $100M was written in the lease by previous, well-experienced landlord and assigned to me at purchase.In my research, I have had a difficult time trying to nail down exactly what the premium difference may be from $100M to $50M but with the recent surge in prices, the best data I have so far is in the range of $750~$1k per Million of coverage.... so anywhere from ~$40~50k/year.