The conditions triggering the transfer of possession, first to the tenant then back to the landlord, are usually detailed in a lease.
Because they convey ownership rights, future interests can usually be sold, gifted, willed, or otherwise disposed of by the beneficiary (but see Vesting below).
Because the rights vest in the future, any such disposition will occur before the beneficiary actually takes possession of the property.
[1] Vesting means granting a person an immediate right to present or future enjoyment of property.
This rule aligns with the policy that a person should not be allowed to sell a thing that he or she does not own outright.
This type of future interest follows a fee simple subject to a condition subsequent.
This type of future interest follows a fee simple subject to a condition subsequent.
To see why, consider that in order to retain Blackacre, A must continue to perform under the terms of the grant (by not drinking).
If A fails to "not drink", that condition will trigger the subsequent loss of A's rights in Blackacre.
A remainder is a future interest in a third party that vests upon the natural conclusion of the grant to the original grantee.
Note: a different result would be reached if the grant was "O to A for life, then to B, unless B and C are not married (at the time A dies)".
An executory interest vests upon any condition subsequent except the natural termination of the original grantee's rights.
Finally, the interest may shift based on a wholly external event, for example, "To A, but if the Cleveland Browns win the Super Bowl, to B".