@Diana Mulvihill A lot will depend on your local market and competition.

Looking forward to hearing from local investors in the area!

This was a local buyer.  

When you go from a single family to a Duplex, it becomes "comercial" property and according to (Michigan) the local building dept, I had to hire contractors. 

@Allie McAlister I'm looking to stay local to begin with.

My thinking immediately turned to researching local rental costs per square foot to determine income potential with triple the current square footage.

The problem with apps running comps is that they can't see inside the homes (or smell them lol), or evaluate the exact location, or understand the local market on an intimate level to know what's next door or around the corner and predict the market value and ARV accurately like only an experienced local Realtor, appraiser or expert investor can.

What’s required for success in this is deep knowledge of real estate in general and the area in particular; experience in real estate and the local laws, etc.; and capital to pay for options, marketing, legal counsel, accounting, tax advise, etc.  

Quote from @Noah Laker: I'm a local broker and investor, and manage 100+ Airbnb properties for clients.

I would recommend looking for local FB investor groups, most areas have them!