Any advise on materials?

Additionally, I’m unclear on how their ARV analysis is conducted since most properties can be found on Redfin or Zillow — does it involve an in-person visit, or is it purely data-driven using comps and suggested repairs?

In Georgia my average materials cost on a new roof is $2,850.

Also in 2022, Ford increased the cost of the Lightning by upwards of $8.5K due to (ahem) "more expensive materials".https://www.caranddriver.com/news/a40848342/ford-f-150-light...

Only thing I'm not sure of is the old countertop material, but it does look look in the photo. 

Not necessarily land, as it is very costly to build there as all materials except for some concrete products have to be shipped in.

The local hardware stores and big box stores sell materials, they hire local workers.

He networked with investors and offered to pick up and deliver materials, then he cleaned and secured the worksites every night.

I have been involved in litigation in the past when a subcontractor ordered materials from China and the formaldehyde levels in the products were not satisfactory to the buyers of the units when they did their own testing and they filed a multimillion dollar lawsuit. 

These "investments" were pure speculation driven by a set of economic conditions which no longer exist.