In addition to what the other agents wrote below I would add that all you need is a note from a doctor stating that you need the animal. The note does NOT have to state the reason why. You can choose to share your medical needs with others, but it's your choice, not required. With the note of your doctor, the association must allow it. Most associations and their management companies have had experiences with these kinds of situations and should be well aware of the laws protecting people with disabilities.
Also, if you require special services such as a visual door security alert (as opposed to a buzzer) to let you know you have guests waiting for you in the lobby, you may install such a device at your cost as long as you return the system back to the way it was when you sell or permantly leave the unit.
Best of luck!