This spreadsheet would obviously need to be pretty complex as it would need to keep a month by month tabulation of monthly payments on each property (assuming a loan) as well as principle being paid down and factoring that into total debt vs. equity, so on and so forth.I'm hoping that example gets the list across.

As to the Two to buy out the One, that's easy enough in principle. 

I agree with the principle of the 'one thing' in that you should focus all your attention on one area to build your business.

Assuming you received a dollar for dollar match from the employer up to some point, I could imagine after the 10% penalty you end up with a glorified savings account with roughly your principle contributions left (again this takes into account that you will pay taxes either way, now or in the future). 

Or....Use the down payment assistance, take the credit, and pay down 2nd while using the profits to pay it off quickly, then principle.

*Full Disclosure - I am a Rent Manager Employee*Rent Manager is actually a full accounting software suite using GAAP - generally accepted accounting principles.

Since I'm older, passive income without losing principle over the long run for a portion of your funds and some in the more risky pig in the poke rehabs makes sense.

I think you're going to find it extremely hard and unrewarding to reduce the entire economics of an area into one fundamental principle.

It would make sense to me to take on 'green' building principles especially thinking of the monthly savings.But does going green in your development properties also being on the extra costs of having to have specialist do certain parts of the job because it is a 'green' job in whatever aspect where a normal gc wouldn't be able to install something specific?

I say apply the usual principles of business in all real estate situations.