Is there something about the yellow color which makes more it effective than say a white paper, brown paper or blue (my personal favorite)?

Good blue collar is good.

My wife does all the cleaning between rentals.But to answer your question, the closest thing I have found to a centralized database is a site called blue collar housing without the spaces. 

I just did a portfolio in Blue Ridge, TX similar to this earlier this year. 

Some more positive factors are stability, relatively well-behaved tenants (especially compared to "blue collar" neighborhoods in the US - the concept of "war zones" really does not exist in Japan), and a mature market.

If you get an upgraded membership, there are calculators on BP under the "Analyze" tab of the blue navigation bar.Otherwise, a quick google search for "real estate investment calculator" gives a ton of options:http://www.goodmortgage.com/Calculators/Investment...http://investfourmore.com/rental-property-cash-flo...There are two.

It's been nearly two years since I graduated from college with a degrees in economics and psychology, and my time since has been split between two blue chip corporations in the energy space. 

I'm in Los Angeles, and I'm wondering if you pick owner occupied areas to go door to door knocking, or blue collar neighborhoods, etc.

The map turns sharply from orange to blue around Camden, where the difference between white and black communities seems almost like it has a distinct boundary.In Lakewood, the fastest growing municipality in the state, the town's exploding and largely white Jewish population appears to have settled in an entirely different portion of town than the Hispanic and African American populations.The map was developed using a cartographic interpretation of the 2010 decennial Census -- the most robust dataset available to analyze the changing tides of population in the United States.The data was derived from Census race data parsed down to the Census block level, which typically span only a few municipal blocks in most areas.

Rockdale is a depressed blue-collar town that hasn't been able to rebound since the main employer (Alcoa) closed its plant there.