Multifamily: How to determine # of units?

[Harrison Smith]

I have seen general questions and uncertainty from various people about multifamily properties and how they are classified during the application for a mortgage. There seems to be some ambiguity in determining the # of actual units in your prospective property, and many properties have convoluted layout or usage. Some who ask this question can be shady persons trying to skirt the law, but I have found many honest requests for help, only to be barraged with clearly bad opinions for answers. 

Can somebody give an exact response that always holds true on how this is determined by your lender, county, city, etc.? Is it the number of kitchens? Is it the number of paying tenants? Is it the number of exterior doors? Is it the intent of use by the new owner? Is it the number of addresses? Or is there a definite legal/tax status given to each property?

I would love to have the answer for those who need it.