Each room could be rented to an individual: Active Duty/Reserve/Guard, college students, young and single professionals, etc.I spoke with a highly recommended property management firm, and they said they only rent per unit, not room.

Talk to your CPA to confirm but those expenses you mention are all considered Operating Expenses and can be  written off,....not sure about the PMI though.

Gross rent less vacancy (5%), less reserve budget (5%) less property management fee (5%) minus all operating expenses = Net Operating Income. 

Do you have enough emergency reserve to stay put without having to fire sale your asset and risking an even worst?

I don’t have much in reserves but have good equity in the rental and in my primary.

Please note cash reserve requirements; If the borrower has 1-4 mortgages, an additional two (2) months for every other SFR investment property and second home is required and additional six (6) months for every other 2-4 unit investment property and second homeIf the borrower has 5-10 mortgages, An additional six (6) months for every other investment property and second home.

Long term goals are aligned and I have no reservations regarding decision making or our ability to define the partnership roles.

I would build your reserves first. 

I planned for both present, and future, with enough risk controls in place (i.e. cash reserves, etc...) to cover my tail.

At a minimum. the investor needs to cover all monthly, debt service, taxes, management fees, expensive, and reserves out of the monthly rental income.