Other than that they are doctors and engineers (at prominent hospitals and companies)...

Was able to house hack for a year successfully, gained a lot of experience in being a landlord, managing tenants, writing clear leases, living with a roommate, learned how to strike deals with the doctor across the street when desperate to find parking for my tenants and I.

I'd rather rent to the doctor than the guy who makes money trading cryptocurrencies. 

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.

Simple they own a business, or a doctor surgeon, or high level corporate exec, sold a business, etc.These people already have tons of income and money they just want something more safe and passive to outpace inflation and park the money.    

Maybe more doctor like people who do not have time to find investments, but trust YOU.

We will be asking for a doctors not and vaccination records for the dog.My main concern is the off chance the dog does bite someone and there is a lawsuit.

My BIL and his wife are quite well off, he a retired doctor, she a high level executive, a Senior VP with an international bank recently assigned to Singapore.

I have 2 vegan acquaintances who are doctors.

I have rented to a doctor for 9 months, and a displaced fire victim for a year.