Fair Housing Laws may require you to allow service animals. Service animals are not considered "pets" so they are not restricted by standard pet policies. You can ask for proof that the animal is "prescribed" by a medical professional or by a mental health care provider for emotional support animals. You cannot, of course, ask about the tenant's disability or diagnosis specifically. You also cannot charge extra pet rent or a pet deposit like you might for a pet. You may not have to provide accommodations if you have few rental units, are renting a single home without a broker, or are renting a hotel room. You'll want to make sure you comply with the laws. Contact a lawyer or your local fair housing office if you have questions.