First I would go to the Building Dept and see if the existing garage is allowed to be converted.

The purpose of this test is to ensure that the property generates enough rental income to cover the property's mortgage payment, including principal, interest, taxes, insurance, and homeowners association dues (if applicable).Key Points of the FHA Self-Sufficiency Test:Applicable Properties: The self-sufficiency test applies only to 3- or 4-unit properties being purchased or refinanced with an FHA loan.

We are also in an area with a low entry point for home buyers so someone thinking of spending $2000 or more for rent is also in the market to potentially buy a home as well which makes the "higher" end rentals a bit tougher to fill except for folks that are building their Dream home and not done yet or in OKC for the short term for a job or family situation.  

The metrics for long term growth that made investors turn to Columbus still hold true and most of the job creation projects, like intels micro chip factory https://time.com/6140476/intel-building-factory-ohio/ haven't even been completed yet. 

Avoid properties on main streets (traffic noise, avoid homes near freeways (smog/traffic noise), avoid homes without garages if most other homes have garages, avoid being in airport flight paths, avoid over building or over rehabbing for the area comps, know how to properly and accurately estimate ARv and rehab costs, and have money lined up in advance.

While income is important for any startup, at Connectlinx, we focus on building strong relationships with our users.

So you’ll owe taxes on any amount you sell over $68k minus capex.

How will appraisers, lenders and tax authorities account for this? 

The second phase of the plan is to build an ADU.

I'll echo what the others have said - not a requirement but also depends on the details of your purchase, particularly the rent amounts for the units in the building.