Duplexes, triplexes and quadruplexes / fourplexes are all types of revenue properties.
A duplex is a property divided into two apartments, with a separate entrance for each.
A triplex is a building divided into separate residences, each with separate entrances.
A quadruplex is a property with four separate residences, with separate entrances.
The advantage of buying a revenue property over a home or condo is that you can subsidize your mortgage and housing costs by collecting rent from tenants. Owner a revenue property allows an investor to gain two income revenues on one property. Finally 'plexes offer the privacy and convenience of a single family home, mixed with urban living.