Since then it has been all on my brother & I; paying bills / ensuring she has what she needs / scheduling doctor's appointments / tending to the house / etc. 

If they become an ESA by getting a doctor to write them a note you will need to accept without extra charge.

He tested at a 7 which is below the limits that require reporting to the state (10) and his doctor came back and said it was OK to stay their since his comprehensive blood work came back lower than a 10, as long as they were comfortable with it.

A lot of attorneys and doctors will hold property like this with their children or wife as the beneficiary in case of a mal-practice claim.

At some point probably doctors no longer diagnose or prescribe for example....when will that be? 

Medical Doctors go to 4 years of undergrad, 4 years of medical school, and then 4 years of residency, plus potentially more time if they do a fellowship.

Your doctor said to do karaoke or sing the Sound of Music wearing goth clothing on the rooftop to calm all health problem.

I have rented to lawyers and doctors, even a former judge, just screen like you would anyone else and check everything; assume nothing.

Someone needs to be available to deal with the staff and doctors and occasional emergencies.

Having old plumbing that has been doctored over will cause that problem.