In-law Suite - Westchester NY

[Joe Jor]

Does anyone know how Westchester County defines an in-law suite?  Is this a legal description or just a marketing term?  What separates this from a "regular" unit?  There is surprisingly little detail on the internet as it pertains to this county.

For example a 2 family with an in-law suite - Can all 3 be rented out?  Is this really a 3 family property (tax rolls say no based on one I checked)?  Is this a 2 family property with an illegal apartment?

@Adam Cherko - tagging you in case you have insights.

Joe