What qualifies a non-standard property as SFR vs 2 fam or 3 fam

[William Boudle]

I understand in obvious situations, like a duplex is a two family. In my particular situation, it effects our financing opportunities. The bank will not lend on more than a 2 family, and our terms change if it is a single family. 

More than a few we are looking at could "qualify" different ways under different circumstances. 

Is a 3 unit with 2 street numbers (but one is A & B making 3 units), and one unit unfinished, able to be considered a 2 family? It clearly was at one point.

Or how about a lot with two houses but one street address, and one needs to be finished to be rentable, but is being marketed as a multi-family? 

Is there anything that can be done to help sway these decisions either way?