I have also thought about refinancing into a 15-year mortgage so we would be paying more toward principal each month, thus "saving" more in our home if we stayed in it for maybe five more years instead of moving into something less expensive. 

I have about 300K principal left.

One thing you are forgetting is your principal paydown to calculate your full return.

I've got 10 units on 15 year mortgages and LOVE seeing the principal reduction (we are in year 6) and now even with the original 15 years mortgage are cash flowing nicely.  30 year fixed rate mortgages are dang near the 8th wonder of the world. 

Making an extra principal payment by treating it like the P&I I would have paid if it was a 30 year fixed.

Expenses will include items such as repairs, insurance, property taxes, depreciation, mortgage interest, etc.Expenses does not include the principal paid on the debt service.It does include non-cash expense such as depreciation.If the net number is positive - it gets added to your taxable income and taxed accordingly. 

Without an actual principal amount and an interest rate, it might be hard to calculate.

No other amounts are deposited in the account during the year, and no portion of the principal amount of the debt is repaid during the year.

Purpose: The Neighborhood Service District allows for convenience retail shopping, personal services, and professional offices principally serving the needs of the neighborhoods within and around the village center.

All monthly debts associated with car payments, student loan payments, all mortgage payments (principal and interest), taxes associated with any properties you own, home owners insurance, association dues, etc.