The answer is, "it depends." Each town has its own zoning by area and regulations on the size of the unit and it must meet current code or you'll have trouble when you sell. You will have to get a building permits from the town before you start, the cost varies. Have your buyer agent check with each town that you are interested before you make an offer on the property. The Code Enforcement Officers in these towns are very approachable and will help to make sure you don't make a mistake. Please let me know if you have any other questions or if I can help.