A duplex is two residences under one roof with common ownership. In other words, the owner owns the building which contains two living units. The building has one assessorâ€™s i.d. number. The owner and family can live in both units, rent one out or rent both units out.
Similarly, a triplex with have three units and a fourplexâ€¦well, you get the idea.
As an aside, duets can look like townhouse but typically do not have HOA fees. You need to take a good look at the condition of the unit attached to the unit you are buying â€“ if it is in poor condition, there is usually no HOA to make sure itâ€™s maintained well. In addition, if you need to replace the roof on your side or paint and the other side cannot afford to do the same, your home can look a bit strange until the other side fixes up their half to match yours.
I hope this has helped.
Alain Pinel Realtors
I'm not sure there is an "official" definition (and the use of "Duet" may just be a marketing term); however, I would consider this similar to a Duplex but each side is owned individually and at least one wall is shared.
"Duplex" appears more straight forward: http://en.wikipedia.org/wiki/Duplex_(building)
By the way, this property went pending on 12/1/11 and was classified as a Single Family Residence in the Tax Database (not a Condo or Townhome).