Many of the surrounding communitie are up and coming with a lot of developments happening. 

Generally larger commercial properties and shopping centers are easier to classify with hard and fast rules, but to the points above the residential areas really move very quickly and have way more nuance than most people care to admit.zip codes are generally way too large for my liking at least in my market to provide any kind of insights other than macro level economics but even then highways or rivers that cut through a zip code can end up with totally different trade areas.we can get pretty granular with cellphone data and with grocery center data to understand the trade areas and their true boundaries, but that kind of data pull is generally only cost effective for investors doing larger scale projects or developments, and honestly we still just end up getting on the ground and feeling it out, so I generally tell people that the money is better spent on a plane ticket and weekend trip in the area you are looking rather than any kind of "trade area" level data studies.and generally B class in 1 area means something different than another. 

They are developing along the river so a lot of upside here (look up hazelwood green).

Thats a lot of work that a company would have to do and they would want their money back on the development costs.

I looked into this at more than one occasion, because Milwaukee has such an old housing stock, everything is 60-120 years old.Most of the new apartments we see are 4 and 5 star developments with very high rents, this allows to offset the high cost of construction a little better.

As others have said, the best thing your son can do is run far from this deal, buckle down, save his pennies (he probably already is doing this), house-hack, and improve a property with sweat, hard work, developing a DIY skillset, and self-managing tenants. 

After analyzing hundreds or even thousands of deals, you develop an intuitive understanding of not just the numbers but their sensitivity.

OK being a life long CA and selling and developing land here for 50 years..

I'm trying to understand how they collect data so as to develop the best comping practices.

Too many people are sleeping on this.Kentucky Economic Development has many site ready properties in smaller areas that are ripe for rentals.