Someone did recommend to borrower money from a private source. 

And 36 Other Key Financial Measures by Frank Gallinelli (This one really gets into the numbers.

In my opinion they are one of the only sources of "borrowed" funds that a bank will allow on a mortgage application without having to jump through lots of hoops.

We currently have one property that is doing well and we're looking to spend some of my time adding to our investment portfolio.There is a duplex in the town next to us that looks great and appears to be turn key.

@Cameron Belknap FHA loan rules in HUD 4000.1 mention not counting the basement as part of the Gross Living Area; however, part of the FHA requirements found in HUD 4000.1 includes a section on “converted spaces” which states:“The Appraiser must treat room additions and garage conversions as part of the GLA of the dwelling, provided that the addition or conversion space…is accessible from the interior of the main dwelling in a functional manner; has a permanent and sufficient heat source… and was built in keeping with the design, appeal, and quality of construction of the main dwelling.”Furthermore,“The Appraiser must analyze and report differences in functional utility when selecting comparable properties of similar total GLA that do not include converted living space.

I don't want to cause trouble with them obviously, so making sure I am allowed to rent is key.

Most of it is "turn key" updated.   

Their permission with their schedule known by both parties and you have a key to their place. 

@Michael Garofalo Unfortunately I'm not the best source of info regarding B-class neighborhoods... as for inventory, I can only relate that in my experience, the MLS seems to have dried up for small multis-- I'm sure they're out there, just not nearly as plentiful as they were last year.  

The key is to hound the First Sergeant and Sergeant Major.