It's like a doctor if he becomes sick, can surely try to cure himself but it's good practice for him to get checked up by another doctor.

We are also home to some of the best hospitals in the world which benefits investors in str's, because of the nursing/doctoral programs here and travel nurses are some of the best tenants to have as they typically are only at the rental to sleep. 

I don't think anyone does except this random "doctor" in Florida.

P.S. 1 - I'm not a "doctor living in Hawaii".

I am fine with the Emotional support animal if it’s a true need; So I requested from the tenant a statement from a doctor stating his need for a emotional support animal (ESA).

If their letter is from a doctor, you should probably accept it. 

If the uncle stays, ask for documentation from a real doctor, not an online site.The bigger concern is the uncle. 

For all I know, if the online reviews are doctored, then I can't really trust the references they provide. 

You denied him because he misrepresented himself on the application.You have the right to ask any tenant or applicant to provide a letter from their doctor stating that they have a disability that benefits from a service animal.

@Andrew Curro, I know that there is a doctor's loan for 0% down that can be obtained.