We developed this out of necessity for our own investment planning as we simply could not find a portfolio calculator online that also allowed for this. 

I also read the opposite argument here http://www.reiclub.com/articles/get-real-estate-license in the article he also says he did not realize the importance of having insurance into well after he had several properties and myself I thought having insurance would just be an automatic necessity (he called it "seeing the light") maybe their is a pro to having a license.

We do pay for garbage pickup (absolutely a necessity in KI Sawyer) and water (because the buildings we have are not metered separately).

I self managed out of necessity because my area has no fully operational property managers.

Outside of the law what are the necessities to have tenants in a duplex pay their own utilities.

My true goal is to earn enough cash flow to 1) cover my necessities and general living expenses and 2) replace my W2 (I have the approximate numbers for these goals based on my own personal ambitions.)Based on your comment, it sounds like I should strive to own high quality real estate in medium-high barrier to entry (read desirable, appreciating, etc.) neighborhoods.

I have extensive experience with 37 Signals' Highrise (cheap, fast to implement, fast learning curve) but have also looked at Salesforce and heard good things about open source programs like Sugar. 4 - The necessity of working together in the same office vs virtual operations.

More effectively monetizing each of your transactions is not only smart but may be a necessity in the post-NAR Settlement era.

Necessity brought out the creativity of an energetic young bi-lingual agent investor and I responded.   

These apps make tracking the financing so much easier, plus they handle online rent collection (a necessity if you don't have a property manager!)