There is a
real estate company in Australia (duplex.com.au) that specializes in designing and building only duplexes. They have a six step process leading a person from duplex plan design and property site evaluation to the actual construction and tracking of your duplex. This is a construction niche that we feel is under-served and is open to growth. We will keep you updated on other companies that have this specialization. If you are developer with this specialty, make sure you email us and let us know about you!