It has a large enough MIL suite with own kitchen, BA, BR, and own entrance but all under one meter.

My fiancé and I live here locally in Denver as well and just bought a SFH that is basically a duplex since it has a separate entrance basement with a full kitchen.

Removed the door, put in a wall, added cabinets/fridge, painted, installed a kitchenette, and created a second entrance for us to access the back yard we now have a little duplex.

Separate entrances and separate renters is what will define it as a duplex.

Once relocated and settled in I am hoping to do a house hacking/remodel type gig and renovate a bedroom into a separate entrance, mother in-law studio to Airbnb.

We then added a closet to the main front living room and built a wall around the entry to create a seperate entrance for this room, and the converted garage, and seperated the living room/bonus room in the back into two bedrooms, giving us a total of 6 bedrooms.

However, it got to the point that having "roommates" has become a problem as I've gotten older, and I am now under contract for House #2 (also in Arlington) that will have a fantastic mother-in-law suite situation that has a separate entrance.

You can find the occasional home with a separate entrance unit ( mother in law suit).

What I've done is look for 2,000 sq ft 3/2 homes that I can split into a 2 units with separate entrances.

Best to find one with an ADU already built in, or very easily converted, preferably separate entrance and parking.