To own an "interest in real estate," one must own:

To own an "interest in real estate," it is necessary to possess some part of the bundle of rights associated with the property. The concept of the bundle of rights refers to the various rights that a property owner has, which can include the right to use the property, the right to lease it, the right to sell it, the right to enter it, and the right to exclude others from it.

Owning an interest in real estate does not require full ownership of all rights, as this ownership can be fractional or limited in scope. For instance, a person could own a leasehold interest, giving them the right to use the property for a specific duration, without owning the underlying land. Similarly, a co-owner might share certain rights with others while retaining some rights exclusively.

Therefore, the correct answer emphasizes that one can have an interest in real estate simply by owning some of the rights associated with the property, rather than necessitating ownership of every right or the physical structure itself.