@Dustin Pavlik Like @Julie McCoy said, check your local laws. If it passes that test, I am in agreement with what @Scott Jackelen said about doing both units.
I have opened 3 duplex properties in Columbus OH, in the last year and manage all units as Short-term rentals on Airbnb. If you use the "Combo listing" strategy, you can see huge returns by dynamically pricing the units correctly to match demand. On high demand nights, being able to house large groups last-minute yields amazing returns. Then on less demand nights, the smaller units are very attractive to smaller groups. We have a duplex in a "developing" part of town, that each unit would LTR for $800/month. We just got it booked for an upcoming music festival weekend from a group of 12 for $800/night for both units.
Having the units so close together, you can create economies of scale by sharing internet service, sharing laundry service area, sharing supply storage areas, and your cleaners should charge less to clean 2 units right next door to each other.
I would also understand wanting to hedge your risk on STR, by keeping one unit as LTR, but you must then find "the right LTR tenant". Some renters may have issues with having a constant rotating cast of renters next door.
It also depends on the actual property design. I would stay away from up/down duplexes, and stick with sid-by-side, or twin-signle. Also the newer construction the better. Newer construction, and more separation for each unit will result in less noise complaints from and for your Airbnb guests.
Good Luck!