Oral rental agreements are usually binding. The "statute of frauds" requires rental agreements for more than a certain length of time (normally one year) to be in writing. But the common month-to-month rental agreement may be either oral or written.
How can I prove an oral rental agreement?
By testimony of the people who made the agreement or heard it made. If there is a dispute as to what was said, then the judge or jury will decide who is telling the truth. People sometimes say, "It's your word against mine, so you can't prove it." Not true. If her word is believed and your word isn't, then she proved it!
That is why it is better for everyone if the agreement is in writing, even if the law does not require it to be in writing. When you write everything down, sign it, and keep a copy, you can prove later what was agreed to without worrying about who is believed.
How do I write up a rental agreement?
There is no formality required in writing a rental agreement. Just write on a piece of paper the names of the landlord and tenant, the address of the place to be rented, the monthly rent and when it is due, and whether the term is month-to-month or some set period (like six months) - and then have both parties sign it and keep copies. Those are the basics, but you should also write down anything else that is important to you, such as the amount of any security deposit and how clean the tenant must leave the place to get the deposit back, any repairs either party promised to do, and whether pets are allowed.
You may obtain a form agreement from a book store or stationary store, or from your local apartment owners' association. But these forms are not adapted for your particular situation. It is better for you to see a lawyer who specializes in real property matters. He or she can draft a lease or rental agreement that suits your needs. Also, it's a good idea to form a relationship with such a specialist now, before trouble arises, so you have someone to call when trouble (an eviction, a lawsuit, etc.) arises - as it probably will. GotTrouble.com