I do think you need a separate entrance option or at least two entrances in a four-plex to make it easier on the LTR tenants, but if you are open about it form the start, everyone gets it and you choose the unit composition based on which ones will be STR or MTR.

I would like to use this life adjustment as a catalyst for my entrance into real-estate. 

I'll include all details below.THE LOCATION: The hotel is conveniently located in the breathtaking Smoky Mountains, just minutes away from the Great Smoky Mountain NP entrance.

Does the side unit have a separate entrance like a mother-daughter? 

Look for multis with separate entrances in different areas like one door in front for one unit and a door on the side or back for another.

How about a house with an ADU, or a basement with a private entrance that can be rented out?

Everything suddenly makes a loud & notable entrance.  

If privacy is a concern with young kids at home, you might look for properties with separate entrances or a layout that keeps your space distinct.You mentioned having substantial equity in your home, which is a great resource.

I have personally stayed in one of these places where the main house is separated, and only the basement space which has a walkout entrance, its own kitchen, and two bathrooms would be rented out an Airbnb.

Like @Russell Brazil said there are general things that need to be in place.One that stings a lot of people is the main entrance door.