He said, on more than one occasion, that "Doctors and Nurses" rent the homes he sells.

Specified Service Trade or Business is defined as traditional service professions such as doctors, attorneys, accountants, actuaries and consultants, performing artists who perform on stage or in a studio, paid athletes, professionals in the financial services or brokerage industry and “any trade or business where the principal asset is the reputation or skill” of the owner.

When your wife interviews the CPA, make sure they are real estate savvy.CPAs are like doctors and lawyers.  

I am a 44 y/o full time optometrist (eye doctor) practicing and living in Northern Indiana.  

Carpenters and car salesman can learn as an apprentice, doctors or attorneys or CPAs must learn from professors and then may go through an apprentice program, professionals have a higher degree of education required than trades.

Google to diagnose their illness instead of an actual doctor?

Ryan,I have worked with Anthony "AJ" Wong over the years to help a lot of Doctor's, Surgeons, and a lot of medical clients get into some great homes in CA & Oregon. 

While there are other avenues for better returns, most of these owners are professionals who are not interested in learning about real estate investing (several doctors, nurses, attorneys, engineers, etc.) 

I know there are some patients that do get prescription from their doctor for certain ailments (glaucoma).

I had a client ( was a turn key operator in LA that I funded) he was a doctor in the Marines..