I am considering building another structure if county will permit.

The hardest thing I have seen about this is utilities and the permitting.

@Nick Seginowich I don’t know what the energy code is like where you are looking at the house, but pulling a permit for a full re-hab may trigger updating the insulation, air sealing, windows, etc to a higher efficiency (which can be costly).I would make sure to do your due diligence before pulling the trigger

Never pulled permits like he should have and showed me a fake GC certificate.

Never pulled permits like he should have and showed me a fake GC certificate.

Helping to keep permit costs low is the best course of action in my opinion because that will help building in the area.

If you haven't done this already, check out the zoning code for the locality and see what land uses are permitted by right or as a conditional use for this parcel. 

You could check the permits to see who the listed owner is.

Spiral would also require opening up the ceiling which gets into cutting joists and reframing which may require permits and inspections.

I found the deal, analyzed the deal, worked with all the vendors to get them lined up, worked with the city to get through permitting, negotiated the deal as the buyer's agent, and am the boots on the ground for the redevelopment process.