You can prove an oral rental agreement by the 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 his word is believed and your word isn't, then he 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.