Just FYI, if a house is ZONED in a single family residential zone, you would have to go to the zoning department of Woodbridge to make an application for a variance to convert to a 2 family. However, it's my experience that most zoning boards will not allow this to occur. (I am on a local zoning board myself so I know something about this). The only way to find out what the zoning is, is to go to town hall and speak to the zoning official.
Please DO NOT consider doing a conversion without the proper approvals. It's illegal, unsafe and can get you into a lot of hot water, with heavy $$ penalties if the conversion is discovered and was done illegally, including making you convert back to a SF home.