@Mike Lambert That is highly dependent on a multitude of factors like size/luxury class/location/housing type/owner restrictions/etc.

FHA allows the construction or renovation of an ADU on the property by refinancing into a 203k loan, but the property must remain your primary residence.This stuff is subject to change, lender specific, and subject to other factors.

Obviously, two factors are responsible for what will likely be more than doubling our money in 3 years.  1.

Yes, I use Zillow reporting as a start and look at other factors.

STR management is 20-25% (I would recommend self managing or getting a VA), since income is higher you could probably get away with 5% for maintenance / cap ex but remember you need to cover utilities and cleaning for these units which drives up costs.

I would factor in time to travel to any market, but AZ is relatively quick compared to the east coast. 

. #1 is the primary reason, but #2 does factor in as well.

All of these factors/considerations impact each other to some extent and its impossible to know whats possible until everyone in the group is clear on what they need/want this to look like.Either it sounds like you're on the right path with the line of questioning. 

You may also want to check the Columbus OH market - great macroeconomics with lots of job and population growth along with major companies developing here that drive strong rental demand. 

@John BerjIf cash flow is a top priority, factor in HOA fees (common with new builds) and confirm rent comps to ensure the numbers work.