She feeds me off-market multifamily deals regularly and knows the neighborhoods very well.For medium to large multifamily, Altay Uzun with Marcus & Millichap runs a lot of volume in the market.I’m a principal in multifamily deals around Hampton Roads and like Olde Town Portsmouth, parts of Norfolk, and parts of Virginia Beach.What are you looking for?

TOTAL MONTHLY EXPENSES:  $1,504 (monthly P&I, plus all the expenses outlined above)TOTAL MONTHLY CASH FLOW:  $396 ($1,900 rents - $1,504 expenses)Annual Cash Flow:  $4,751 ($396 x 12)COC RETURN:  9.1% ($4,751 annual cash flow / $52,475 total cash in)Net Operating Income:  $13,691 ($1,900 in rents / $759 in expenses other than principal & interest payments... x 12)CAP RATE:  7.6% ($13,691 NOI / $179,900 purchase price)So, you can see this isn't exactly a home-run deal as far as CoC return goes, but the cash flow is almost $200/unit, which isn't bad.

You are right, if your house was your principal place of business, you could deduct the commuting expense going between your residence and another work location IN THE SAME TRADE OR BUSINESS. 

my guess would be water,sewer,taxes,insurance, maintenance, capital expenditures, common areas (everything but the principal +interest ) 

Paying additional principal each month is a legit interest reduction strategy, just like biweekly payments or lump sum payments.

You won't pay down squat in terms of mortgage principal in the three years. 

Should I use net income to apply towards principal of loan or use equity to purchase more property?

By the end of the term, I would have paid off enough principal that I would not be too worried about being able to refinance again if I held it that long. 

Obviously you won't be paying down the principal but your cash flow will be better.

If in 10 years the rate is 11%, you will have paid down your principal balance significantly and likely inflation will have happened, so your rents will have increase (and expenses), resulting in still solid cash flow.