Why pay off the mortgage early? 

because I was paying my bird-dogs vs having them pay me and just promise how someday, maybe just maybe they will bring the grand-slam of a deal and then I will be paying them oh-so much $$$$$ Seriously, from those buying into this I gotta understand how your mind works, no insult meant, I am genuinely intrigued and baffled because if it's a good deal you can go to any number of investors and get $, not a one will charge you for the opportunity to present them deal. 

. $1300/month, tenant pays all utilities. 4 bedroom one is vacant.

And, it's amazing how many closing costs are junk fees that we as investors need to pushback on paying for ourselves and our clients.

Tenant covenants and agrees to pay interest at the maximum lawful rate or eighteen percent (18%) interest, whichever is less, compounded annually, on all unpaid Rent, damages, and other amounts owed by Tenant, excluding late fees, from that date of Landlord’s final accounting until such time Tenant pays all such outstanding amounts.

We will be paying nearly $50,000/year in property insurance.

But now 50% are not paying.

Right now, the best offers around me are for some 1.3-4 million, that only generated around 100k per year gross, so there would be a high chance of not cash flowing, and paying money, especially with a commercial loan (these buildings have more than 4 units).I was thinking that although the rental itself does not generate money, I would be able to deduct the mortgage interest, and depreciation from my personal w2 income and would be net positive.

You pay a down payment, closing etc.

I LOVED getting a loan through DR Horton on a DR Horton build, that I had to pay for a DR Horton appraisal.