At this point I know their income is sufficient, they have indicated they dont have a criminal issue, bankruptcies, and evictions. 4.

Population growth, job diversity, and low DOM (days on market) are significant indicators.

The more cash flow a property has is an indication that the risk that asset has is greater. 

Ideally, you want to look for markets with a growing economy, diverse industries, and growing population that indicates strong rental demand.

I'm currently researching the market, trying to get an understanding as to where these different areas are located in the cities.Any indication is welcome!

There was no market data indicating there was a market for $3K 3 BR rentals but that was merely because nobody ever supplied the market with the inventory.

But there's no body of case law indicating that to be a concern.

The historical appreciate indicates it will not keep up with inflation and therefore loose value in inflation adjusted dollars.  

I have looked at Hopatcong however despite allowing STRs, it has language that requires the STR to be the principal residence of the owner as indicated by something such as a diver's license.

We keep seeing conflicting views but my personal experience with buyers indicates that the outlook is positive.