Is it permissible to take "khalw al-rajul" (key money) from tenants in commercial shops, and then set a mutually agreed-upon rent for life?

It is permissible for the owner to take a premium (khaloo) from the tenant, provided that this premium is considered part of the agreed-upon rent. In the event the contract is terminated before its term expires, the rulings pertaining to rent shall apply to this amount. Scholars have unanimously agreed that it is not permissible to lease for an indefinite period (lifetime) due to the ambiguity of the duration.