Now, I think I know what direction your going in. You said the leasing office told you that you could have a dog "if you could get a letter from a doctor" Then you mentioned that your father sees a psychatrist. That you are going to have your father's psychatrist , write YOU a letter stating that YOU need a dog for "psychological" purposes.
The problem: this is your fathers doctor . Your not being treated by the doctor, and your thinking the Dr. is going to write you a letter

Is your father going to be living with you? Is the dog going to be yours or your fathers??
Because if it is going to be yours, and you are not being treated by a professional, there is little chance a professional is going to write a letter for you, stating that you need accomadations for a "service Dog. AND it is against the LAW to be deceptive . A service dog is not considered a pet. However, you do need docuementation for yourself, from a PROFESIONAL. + you need to be in treatment, in therapy, and have ongoing treatment, proff that YOU need a service animal.
I highly doubt any professional is going to write a letter for someone who they are not treating.