多謝回答。是網上查的，請見內。

https://www.nolo.com/legal-encyclopedia/california-landlords-tenants-service-dogs-emotional-support-animals.html

加州要求必須同意？而且不許額外收費？

https://www.nolo.com/legal-encyclopedia/california-landlords-tenants-service-dogs-emotional-support-animals.html?

Landlords may not require applicants or residents to pay a pet deposit for a service dog, psychiatric service dog, or support animal, even if they do so for other applicants or residents.

A support animal, on the other hand, must alleviate one or more identified symptoms or effects of a person's disability, but there is no requirement that a support animal be individually trained or certified, or that it be a dog. 

看來我下一步需要他提供醫學證明？

When the disability or need for reasonable accommodation is not obvious, a landlord may ask the person with a disability for documentation that he or she has a disability and a disability-related need for the service dog or support animal. The tenant or boarder must then provide the landlord with reasonable medical documentation from a health care provider that confirms the existence of the disability and the need for reasonable accommodation.

醫學證明需要說明：

In California, a mental disability includes any mental or psychological disorder or condition--such as intellectual disability, clinical depression, bipolar disorder, organic brain syndrome, emotional or mental illness, or specific learning disabilities--that limits a major life activity.