3) itemize your expenses bc you may find out the 50% rule is not accurate for your area. 4) make sure you account for a Third party property manager (this will minimize your issues with non-payment and other tenant issues) I would double check those figures to make sure they are accurate.

How does one estimate the fluctuation of rental income on a cash flowing properly accurately.

How does one predict the market accurately to make the most intelligent assumptions about the economy for more efficient real estate investing?

There are always a million questions about whether or not Zestimates are accurate and whether they should be used for reference.

How accurate is this info?

Data outside a mile or so becomes less and less accurate, depending on the location. 

Those numbers sound accurate. 

@Charles CarilloPublic records state that the owners live in the house, which isn’t accurate (homes are boarded up, some have city notices on them).

Of course of all of this relies on my assumptions being accurate...something that is impossible to project!  

They aren't high, they're accurate.