NJ Green Card -Two Unattached Duplexes on one lot - required?

[Sunny Burns]

Above is a survey of my property. The Front House is a duplex and the rear house is a duplex. Together the lot is considered to be a Four Family Home.

I am trying to decipher the http://www.state.nj.us/dca/divisions/codes/offices/housinginspection.html website. I believe it says I am exempt since it mentions that only "buildings" with 3 or more dwelling units require it, and I only have "buildings" with 2 dwelling units. Anyone have a property similar to this? Another reason I believe this to be the case is because when I called to ask the status of the green card when I was first thinking about purchasing the property, they told me that this property has never been registered with the, The property is at least 75 years old, I find it hard to believe it could have gone on without one for this long, if it was required... please chime in.