Your policy can require, for example, that you are provided a current Veterinarian's report on the health of the animal; a letter or form from a "reliable" source such as a local medical or social professional verifying that the tenant has a "qualified" disability, and that the animal performs a specific task, or alleviates a symptom related to that qualified disability; tenant must clean up after the animal in common areas; no offensive odors can emanate from tenants residence; and both the vet report and verification of tenant's need must be updated annually. 

Many space related jobs will live in Nona and commute, not to mention all of the tech and health care, so it will continue to be attractive and appreciate very well. 

This inspection includes a wide variety of health and safety checks.

My question is it legal for me to deny an applicant in this situation because of the disruption to other tenants, threats to their health and safety and additional costs? 

I have been contacting the county health department for permits on the septic system.

I'm a hands-on person myself, that can build a home, garage, if need be, but time and health is more important.

Check with either the building dept or the board of health. 

A taxpayer who fails to meet the Section 121 ownership and use requirements or the one-sale-in-two-years requirement is eligible for a partial gain exclusion if the principal residence was sold or exchanged by reason of(1) a change in place of employment;(2) health; or(3) unforeseen circumstances [IRC Sec. 121(c); Reg. 1.121-3(b)].For each of the three situations where a partial exclusion may be available (change in employment, health reasons, or unforeseen circumstances), safe harbors are available.

The Mayor of this particular city, building inspector, counsel, and health inspector were all aware of this house -- received a Thank You from them when it was done. 

You cannot ask why they need the animal, but you can ask for a letter from a qualified mental health care professional stating they need that specific animal.