By definition, a duplex implies two. Commonly, a duplex is a pair of homes joined by at least one wall.
A condominium is a unit that is owned by a single owner, who also owns a share of the common areas around the building, including the building. There may be a few or hundreds of units in a condominium complex.
A duplex is a
single house which is owned in fee with two units that share a common wall. It can be owner occupied with multiple owners dwelling in the two units, one unit rented to tenants or both units can be rented. The important factor when comparing it to a condominium is that there is a single owner of the property by deed, in fee.
Generally, a condominium project is a form of fee ownership by which several owners share ownership of a building(s) by each owning their respective units. Condominium projects must be declared as such under state law and are
governed under the strict provisions of state condominium laws. In addition to their unit, each owns a proportionate interest in the land that forms the condominium property and common areas of the condominium such as pools, recreation areas, game rooms, community rooms, elevators, stairwells, corridors, streets, surrounding land, laundry rooms, and unassigned parking areas. By the acceptance of their unit deed each unit owner agrees to have their unit subject to the provisions in the Master Deed. Although a condominium is governed by statutory law, can promulgate rules and regulations and assess monthly maintenance fees, the ownership of a condominium unit is considered a fee simple estate.