Building Triplex/Quadplex "Townhomes" then selling as SFR

I've recently been looking for my first investment, there is a local area that has town homes ( four units in the same building side by side). I spoke to a local real estate agent about purchasing the whole "building" with my intentions in living in one and renting the other three out. At this point he informed me that each individual "unit" inside these buildings are considered a SFR.. So I dont know the history of the building but is it possible someone had these built as a "multifamily" then sold each unit individually? Is anybody familiar with a situation like this and can shine some light?