Building extension

[Amy Zhang]

Hi all,

I am looking at a house in Brooklyn, NY. It is a two family house with an extension. How do I find out if a building extension is legal or not? Should I assume it is illegal if no permit is found on building department website? It also has a small bungalow in the lot with 1 bed, 1 bath and a kitchen. I am not sure its supposed to be a garage or it is illegally converted into a studio. How do I find out? 

Thanks.