Depending on local regulations, you can mix up STR/MTR/LTR. 2) Get systems in place in those exact cities; 2 PMs preferably via NARPM, 2 high quality inspectors, and rotating book of handyman, 1 lawyer, and a credit union contact for leverage along with investor friendly nationwide lenders.

Issues with multiple national carriers leaving the state completely due to state regulations, massive loss ratios, huge increases in replacement cost values/limits due to inflation, etc. 

Part of this is regulations in my city, but after having done it this way, I wouldn't ever want to do it with a single family home.

STRs are an option too, but you’ll need to navigate stricter regulations in some areas.

I'm not sure which places are best to focus on with rules and regulations getting strict in some places. 

While I don't believe that you need a full blown business plan, strict operational budget, timeline, scrum board, etc...

Ensure that you check your state's regulations and requirements regarding security deposits.

Make sure you thoroughly know how the regulators view the way things are being done, before committing to a "creative financing" technique.

There is a lot more state regulations and lending laws change when 5 units or great.

@Hamidou KeitaTo build a duplex or ADU in Tucson, verify zoning regulations, obtain construction estimates, budget for unexpected costs, research market rent and vacancy rates, calculate ROI, consider neighborhood and property value trends, analyze construction timeline, consider exit strategy, and consider a backup plan.