So for the additional three bedrooms, I plan to Airbnb and/or expand the shared-housing community I currently have for women in transition at my duplex .

What else i should ask inspection to look for in addition to below.

Insurance is just an expense to factor into your underwriting just like property taxes.

The house will need a new fence soon, so I'll have to factor that into the scenario.I'm not sure which choice is the best option for me.

In addition to those I would also suggest making a commitment to going to local meet ups and networking events in your area.

I guess it's just too many factors to consider and it easy to get overwhelmed and cannot get accurate info and estimation when I conduct analysis (ex. property tax rate, insurance, maintenance fee, rent, repair, closing cost, etc.) 

One thing to add is that when you buy a new build, your PITI will likely not be factoring in the correct state tax number.

Either way it would be a grey area, selling a house with a different amount of units/bedroom/bathroom seems extreme though. its an auction site, I have seen auction sites miss the fact there was additional lots in a sale.

Additionally, working in a small-town market taught us how to effectively price properties for faster sales without compromising profit.

These are professionals with additional training and a stricter code of ethics.