A duplex house is a dwelling having apartments with separate entrances for two families. This includes two-story houses having a complete apartment on each floor and also side-by-side apartments on a single lot that share a common wall.
The term "duplex" can also be extended to three-unit and four-unit buildings, or they can be referred to with specific terms such as triplex and fourplex or quadplex/quadruplex.
It is a great investment when you consider the benefits that can be reaped. It often comes at an affordable price and makes a great choice for a first home investment. If you rent out the other portion, you may always have a source of income which can be relied upon. You can even cover your mortgage payments and your insurance coverage from the rent you charge.