SFH to Multi Legalities

[Bryan Cavellier]

I am curious about legalities in what I am thinking of doing. Is it possible to make a SFH into a multifamily (2 units). Theoretically I would buy a SFH with some type of mother in law suite or finished basement that makes sense. I would not split utilities of the two units either. Is this legal (New York)? I see properties all the time labeled unit A/B or 1/2 because they aren't split... thoughts?

-Why would I want to do this? I don't have the cash for a 20% down multi-family and am currently in my FHA loan so that option is out as well.