I don’t  know exactly but on that $350K house in Plano I’m gonna guess property taxes are in the $7k a year range.  

You've got your ballpark range (big ballpark). 

Obviously land and new construction, specifically FHA construction, is not popular these days so it seems to be extremely difficult to locate anyone with sufficient expertise or specialization in this area.

For wholesale purposes you will find distressed properties that when fixed are still in affordable price ranges for end buyers especially with where rates are, or work on DSCR products.

I'm in the market rate range so it's not severely under rent.  

There are a couple of turnkey condo's in my area that are within my price range. 

Now some hypothetical numbers that are in the range of expectations

Grow my other business to 150-200K range(gross).

I know a local mentor who has a wide range of RE experience, but with mixed results on her level of success.  

Highest sales on older duplex homes in Marion over the past 12 months are in the $130k-$140k range and they want $118k for the house.