If so, you can count on your "economic vacancy" being a lot higher than what you are projecting due to non-paying tenants, plus higher and more frequent turnover costs.We would really need more information that what you provided. 

For that, a contractor can put something together that requires less energy and wont be thinking their is a possible job coming up...

The key is not to get too sucked in where you are wasting a lot of energy and time.It is probably easiest to just send them the requested letter.   

When the downward economic cycle happens and shifts more to a buyers market then they start buying more.

I've looked and read a whole bunch of articles, and tried to find various economic indicators to see if there are any that linked to it. 

Partnership taxation can be very simple but can also get very complicated very fast, especially when you get into substantial economic effect issues.

A few things I noticed (1) you didn't include gas in your expenses (2) management expense at 6% seems low - I've used companies <10% before and I paid for it (3) billing back utilities via RUBS (Ratio Utility Billing System) is a legal, extremely economical way to bill tenants their fair share on a master metered property, however, make sure your state statues support it and is fairly commonplace with your competition. 

@Kole Kingslien  Guidelines for land contract:- Payoff of Installment Land Contract Requirements When the proceeds of a mortgage loan are used to pay off the outstanding balance on aninstallment land contract (also known as contract or bond for deed) that was executed within the12 months preceding the date of the loan application, Fannie Mae will consider the mortgageloan to be a purchase money mortgage loan.The LTV ratio for the mortgage loan must be determined by dividing the new loan amount by thelesser of the total acquisition cost (defined as the purchase price indicated in the land contract,plus any costs the purchaser incurs for rehabilitation, renovation, or energy conservationimprovements) or the appraised value of the property at the time the new mortgage loan isclosed.

This dramatically increases the economic benefit for the investor. 

Unless there is something on the line for me, I am not going to be willing to invest my energy to learning about it.