I take a map and highlight the streets as I go (red = "A" neighborhood, blue = "B", etc.) just based on my visual.

I've read a lot over the last couple of months, but it's not like the Stock Market where I can sign up on Etrade and buy a blue chip to get my feet wet.

The light blue cells require inputs unique to each property.

Most people in this area are blue collar hard working people.

Although I am not as familiar with the area as I used to be, I DO know that it is convenient to downtown Chicago (290, Blue Line, Pink Line, Metra) and rent ratios look pretty good.

One area could be full of drug dealers and one street over will be well kept homes with blue collar workers.  

As far as I am concerned, a seller will get much better service if I can come back on a bright blue skied sunny day with my professional photographer and snap some nice shots of the property.

The adults will probably be low touch, as long as it doesn't become a post-frat-house affair, and in the marina you need to watch out for that ;)As for keeping several properties in SF as rentals, look you have blue chip assets.

In some "blue states," it takes months of meetings, permitting, and environmental studies before you can even break ground. 

But seriously when someone out of the blue sends me an email like that I normally don't even reply.