The tenancy between the parties is a legal contract. It cannot be changed by one side. The tenant can agree to a rent increase. But if the tenant does not agree to the rent increase, then the landlord must terminate the tenancy. In a tenancy at will, the landlord must then give a notice to quit but such written notice may include an offer to establish a new tenancy for the same premises at the higher rent. If the tenant does not agree to this rent increase, the only option for the landlord is to commence eviction proceedings.