Duration of the lease
A tenancy at will is different from a periodic tenancy there is no specific time or duration of the lease. The agreement may be terminated at any time either by the tenant or landlord for no reason at all, or by citing some reasons. However, the rule on sending proper notice is followed depending on the local laws on the number of days notice has to be served.
In the absence of a formal lease agreement, the tenancy is generally considered tenancy at will. Tenancy at will may also be without compensation where the parties expressly agree that no rent will be charged which happens in very special cases.