DSCR is calculated by using the monthly market rent or lease (up to 120%) and dividing it by the Principal, Interest, Taxes and Insurance Payment. 2.

I add bedrooms and rent by room. 

This will serve as my primary residence and I'm hoping to rent out the other 3 units.

Any advice on how to pick which location to jump on first??

I suspect an Bk attorney would advise you that you don't qualify for a BK.I suggest you consult with a very good real property attorney, preferably one who practices in the area the property, or better yet the foreclosure Trustee is located. 

My husband and I are looking to buy our first ever real estate investment out of state (we live and rent in NYC. we do not want to buy here due to high cost of properties and high tax rates).

The tenant has been a problem from the beginning, such as behind in rent for a year, buys a brand-new Jeep, lies about ex-husbands job, child support, court cases, etc...Now, the house needs a new deck, so I went up to inspect it.

If our intent is to live in a unit and rent out the other unit, will that be a residential or a commercial loan?  

Since it sounds like just a handful of locations, I would experiment with some repair strategies.

I am planning on renting it furnished.