I am curious if I am understanding the only way a tenant in Texas has a right to withhold rent is if there is an amicable agreement between tenant and landlord or if the landlord fails to remedy a problem with the house that impacts the the safety and health of the tenants.I am trying to keep things simple and not complicated on this question. :)

Most cities would likely be best off with limited restrictions (limiting enforcement time & costs) other than enforcing any already existing health and safety laws.

However, after researching it and having her actually do her homework it came to light that divorce, separation, health issues, moving for a job, and a few other extenuating circumstances were the only exemptions for no paying capital gains before 2 years of having it as a primary residence. 

The current owner has owned for 30 yrs and needs to sell for health reasons. 

Whether it’s the economy going sour, or you are growing old, or bad health, you must have a “backup plan”.Many of us hate to talk about having our burial planned out or having life insurance, but it’s something we need to talk about with our families and plan for, and so most of us do.

Obviously, living without electricity may be hazardous to both the tenant and the property.To that end, I would NOT contact any mental health services.

Otherwise, it is mighty dangerous, because everyone wants to be in expert in health, law and taxes, based on their extensive Facebook studies.Your friend has (correctly) heard that the new tax law allows Section 179 for rental properties.

I'm a doctor so these conversations come naturally to me, it's just that your diagnosing the home owners needs and wants rather than the patients health. 

AirBNB specifically recommends language pertaining to allergies and service animals - you can state in your listing that you don't accept any animals (don't say "pets") due to allergies and it being a health risk to you or a family member.Again, definitely look into the laws yourself, but between this being your primary residence, your only STR, and you having allergies, I don't believe you could be required to accommodate service animals.

THIS IS A HEALTH HAZZARD!