In the same line of thinking, when you go to a doctor your first question should be how much do you charge, NOT, can you fix my illness.

I'd argue that if you're buying in a high priced market, some inexperienced teenager who lives in his parents basements is even more dangerous to consumers.The fact of the matter is you've got to go to school for 6+ years to be a lawyer or an engineer. 8+ to be a Doctor. 5 year apprenticeship to be an electrician. 

She was a little late on getting the appraisal to me on a really good loan for a doctor.

Healthcare services such as doctor check-ups and dentistry cost 14% less here compared to the U.S. average.

There are thousands of people in the Bay Area who were middle class, not high earning tech workers or doctors, that are millionaires from owning one to two properties going way back to 1970s to 1980s. 

The tenant also had a note from their doctor saying their kid suffers from X illness and the mold is making it worse. 

It's not just for doctors either.

I'm not that professional but I think a whole house filter would filter particulates like dirt but not chlorine. for chlorine you might need a reverse osmosis system for a specific drinking water tap to eliminate the taste as it's not practical or efficient to put an RO on the whole house supply. if skin issues from bathing are a problem you might need a softener. sometimes when kids have eczema doctors actually prescribe "bleach baths" where a small amount of chlorine bleach is added to the bath water. also many of the water treatment systems can be rented so maybe just rent it while they are there. regardless, proceed with data. water test, pediatrician diagnosis (if it's legal to ask for, no clue), and a system that is right for the application. sounds like the tenant is willing to help out which is awesome.

You could go many different ways with rentals such as student housing, section 8, targeting specific renters such as traveling nurses/doctors.

Just some additional companies for you to consult with in the Indianapolis area -- Hitman Solutions (former contractor at Michaelis) - Acculevel, Jaco, Crawlspace Doctor  -- PM  me if you need phone numbers