Is it easy to make a flexible lease to allow tenant to move out?

[Bryan T.]

Is it easy to make a flexible lease to allow tenant to move out any time they want? 

Let's say you are the landlord who is renting a room/place. Are you able to write a lease that allows a tenant to move out whenever they want? For example, can you write a 6-month lease but include terms that allow the tenant to move out earlier without penalty? Do you need a lawyer to do this or can you just write it down in easy to understand wording?

I am actually also seeking a place to rent so I am asking these questions as well.