All leases whether it is annual or month-to-month should be in writing. And the main reason is that a landlord/tenant need to know what they are responsible for, including security deposit. It’s extremely imperative that all parties know their responsibilities for the unit. An example can be a person is going to be in charge of fumigation while the other tenant is going to be in charge of outdoor maintenance for the lawn. These details are very important and if not put in writing, one party could find themselves getting the short end of the stick. So, it’s highly recommended whatever lease you enter into, to always get it in writing.