Unity of interest, possession, time, title. Joint-tenancy agreement’s legal requirements. (1) Unity of interest is the requirement that in duration, extent, and nature, all joint-tenants must have the same interest . (2) Unity of possession is the requirement that no joint-tenant shall have exclusive possession of the whole property; that each joint-tenant simultaneously with other joint-tenants must have undivided share of the property. (3) Unity of time is the requirement that at the same time and for the same period, all joint-tenants must vest. (4) Unity of title is the requirement that in this single instrument, all joint-tenants must have equal property title.