A security deposit plus any refundable fees (e.g., a refundable key fee), must total one months rent or less. Non-refundable, one-time fees do not form part of the security deposit. The security deposit plus any non-refundable fee can be more than one months rent.
It is important to read the lease carefully, or understand any oral agreement you have. That way, you can determine what forms part of the security deposit and what does not.