Then at the 30 day hearing, he shows up with his father in a wheelchair and asks for more time.

And you eliminate wheelchair bound individuals, or families. 

On brand new site Rentberry you can find amenity called "wheelchair accessible".

Wheel chairs, Canes, WalkersHow big are the bathrooms?

They are looking for at least a CBRF (community based residential facility) which houses 5-8 and it must be wheel chair accessible.  

Many managers still request it however a service animal is identical to a wheel chair and law strictly prohibits the enforcement of verification.

I was wondering if anyone in the Atlanta area can give me a contact for getting a house retrofitted for a wheelchair?  

However he is now in his late 70's and on oxygen, in a wheel chair, unable to leave his house without an aid. 

You can't deny them because of their disability and you should try to accommodate any "reasonable" requests for modification (grab bars, wheelchair ramp, etc.)As Claudio pointed out, there may be funds available to help you set the home up to make it safer.

If we have a tenant in a wheelchair we need to let them put in a ramp but they are responsible for cost to install and remove, I don't see this as anything different.