The news stories about seniors not filling a prescription or splitting a pill to make them go further hit home for me because my dad did those things without telling anyone. 

It's called an easement by prescription. 

I've rented to more than one that were abusing prescription meds.

The verse you mentioned in your original post (borrower slave to lender) is a Description verse versus a Prescription verse.  

I can order prescriptions and have them sent to my home.

Emotional support animals (not service animals) can be asked to show a prescription from a doctor, health care provider or social worker.

@Wayne Brooks My Rays are prescription and I can't grow hair anymore except places it shouldn't grow.

Run an application all looks fine show up to sign lease docs and they have 5 pit bulls that are all "companion animals" 5 prescriptions one for each dog by name and description.  

Los Angeles County, CIty of Signal HIllTenant with anxiety disorder presented with prescription from physician for daily medical cannabis inhalation.My first thought was, 'is that without filters by any chance?'

I'm sure there will be protections in place for prescribed marijuana usage as well, until then, check your local laws but I would assume if they aren't allowed to smoke per the lease, they are in violation regardless of prescription. regarding marijuana usage I say "who cares?".