If he were an adult, perpetrating a crime on a child under 12, I wouldn't touch it with a 10-foot pole.

For example out county has a minimum 2 acre lot size, but also. 300 foot depth.  

Granted that's apples and oranges, because the new homes are larger and all in the suburbs, but as long as you can buy an existing home for half the price per square foot than a new construction home I would be careful with expecting peak appreciation.

I know because we have a 5 acre piece that is worth 200k and if we added a 6k square foot metal building, we could sell it for 450k all day long. 

The roof and attic are the best parts of the house, 0 problems.Main line, laundry line, kitchen line are actively leaking.

I had an AC unit stolen - thieves climbed a 7 foot fence on my Class C house (I didn't have security cameras on this house). 

I’m also scared of the downsizing aspect; we’d probably be looking at going from 1800sq feet single family home to 1100sq foot townhome).

I think if you understand the price per unit as well as the price per square foot in the zip code and nearby zip codes that will give you a good idea of the comparable market analysis approach and appraiser might use.

Cold called this property owner who wants $150K for this 2 bedroom, 1 bathroom 928 square foot home. 

Typically flooring guys charge a flat install per square foot and then more for stairs.