What is a duplex? Homes come in many shapes and configurations, and one type that’s popular with extended families or budding landlords is a duplex. It’s not just one home, but two. The units or apartments may be stacked one atop the other on separate floors, or they may be side by side with a shared wall. A duplex may also be called a “multifamily dwelling,” because more than one family can live in this type of building.

A duplex is sometimes confused with a “twin home,” but they’re not the same type of real estate. A twin home may look like a duplex: two separate homes sharing a wall. But with a twin home, the lot line actually runs through the common wall—so on each side you have an individual home on an individual lot, even though they’re connected.

A duplex is different: Rather than owning just one home, you’re the proud owner of two. As such, a duplex will likely cost more than a single-family home at the outset. However, if you rent out the other apartment, this revenue can drastically offset your mortgage and expenses, and potentially make duplex living cheaper than what you’d pay as the owner of a free-standing house.

A duplex is a popular option for people who want to keep family members nearby or who want a steady income from a rental property that’s not too far away to manage. It can also be a great real estate investment or a creative option for a first-time home buyer, under the right circumstances.

Lisa Johnson Mandell is an award-winning writer who covers lifestyle, entertainment, real estate, design, and travel. Find her on ReallyRather.com