Maybe its got something to do with privacy of the homeowner.  

So they can talk loudly on the phone without being heard, so they aren't hampered by privacy concerns.  

Plus you generally have far more privacy in a house. 

Then I would suggest to learn about real estate investing and crypto currency investing. 

Yes there's no doubt that some of our rights are infringed upon, but honestly after the Snowden revelations "we" (as Americans) basically shrugged away right to privacy, warrantless wire tapping and even killing, etc. 

There's also the danger of the tenant doing things you're not aware of because they're far more isolated and have more privacy. 

People like privacy so a RV type toilet that can be emptied could be used in each suite. 

We have seen crypto currency investing get a lot more interest as well.

The first thing I would suggest is a measure of privacy and humility.1.

For instance, if you write on your mail piece “I know you’re behind on payments etc…”, it can make the seller feel like you’re invading their privacy.