The most common are 1) it’s currently and forever illegal for you to rent it out to two unrelated parties and have two addresses. 2) it’s illegal to do that unless you do “x” (pay the city, add a seperate entrance, whatever. 3) it wouldn’t be legal to be a duplex today but it has been and there fore is “grandfathered” in. 1 is a big deal, 2 is a small deal, and 3 is nothing, a non-issue. 

But if you’re aiming for the highest return, short-term rentals can be a great option.My current strategy is to find a single-family home with an “in-law” layout, something you can divide in two, add a separate entrance, and rent out the master suite or one half of the home on Airbnb while living in the other.

I would not say get a tour, but if you accidentally delivered a pizza to the wrong address you most likely would get someone to open a door to get a peek inside and what the home entrance looks like is typically reflective of the rest of the house. 

Below is entrance 1. 

This sits on the southern entrance to the Smokey Mtn.

I am a landlord renting a 1B/1B in my SFH in California, which has a separate entrance.

One entrance lane on way we took in.  

These are plenty of houses in Chicago that have a furnished 'garden level' basement and often have a separate entrance.

Besides closing the door to the house, we added a mini split for temperature control and a entrance from outside for full privacy.

*Buy a 2-story and take one story, add a separate entrance for a tenant or guest (STR) * Buy a property with a good upside and just take the profit when you sell.