So if your house will make you 1k per month or 12k per year, the Net Operating Income is 6k per year. take the NOI and subtract your principal and interest payment from that.

Despite having a higher rate, you can always send more to principal, but if you go the 15 year, your stuck & the hit to your DTI affects future purchases.

So if all of that stays the same you’ll still (I think) have 6 tenants paying down mortgage principal (however small to start) instead of 4.

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?