I would request a letter from an actual local mental health professional that you can call to verify the ESA prescription, and refuse to accept any online forms they may have paid $20 to download from a fake mental health professional.

The term for gaining an easement by repeated use is a prescriptive easement. 

If the theory is meant to be limited to those four things, then okay, but if it's meant to be a very broad prescription, to encompass stocks as well, the theory doesn't hold water, and thus the advice to buy real estate now is called into question.

Vaping could be used as a delivery advice for this "medicinal" product and thus those with disabilities/prescriptions might be covered as a protected class.

The other point is that those giving details is much like a doctor giving a prescription and if the patient takes the medicine the wrong way or it's the wrong medicine the results can change that persons life or even end it.

Probably won't be solved by adverse possession but might be resolved with either a prescriptive easement or a 'license' for which you pay some nominal fee as the licensee to the property owner.Laws vary by state and can be complicated and expensive to resolve.

A service animal comes with medical prescription from a doctor and paperwork that states the animal is properly trained to be a service animal.

They check all your symptoms over video and even call in prescriptions to the pharmacy.

There is prescriptive language in the International Residential Code (IRC) that you will be able to size your header accordingly. 

Good stuff, I'm still hoping to find something that's a little more prescriptive. :-)