It's also good to point out that lawsuits have been lost by tenants trying to scam LLs into letting them have pets with these doctors notes. The tenants have to prove that they have a disability that requires them to have an animal. Most of these reasons are in the FHA version "emotional problems". These are supposed to be for severe cases where the animal can make a significant difference, not just "wouldn't it be nice to have a dog". It was created for PTSD for rape victims and for people with severe phobias. It has obviously been abused to circumvent the no pet policies in many states.
FYI, if you get a "prescription" for a pet from a doctor for a tenant, check the doctor out, make sure it's legit, and make sure the doc is in a position to actually make a diagnosis for the condition. IE the podiatrist should not be diagnosing mental disorders and writing scripts for it!
Establishing that the support animal is necessary in order for tenant to use and enjoy the residence is critical. Courts have consistently held that a tenant requesting an emotional support animal as a reasonable accommodation must demonstrate a relationship between his or her ability to function and the companionship of the animal. Although the landlord is entitled to ask for supporting materials which document the need for an emotional support animal, federal law does not require the tenant to provide proof of training or certification of the animal. The two courts that have addressed this issue directly - the Court of Appeals for the Seventh Circuit and the U.S. District Court of Oregon - have held that the only requirements to be classified as a service animal under federal regulations are that the animal be (1) individually trained, and (2) work for the benefit of an individual with a disability.