If it's not obvious at the site, talk to any of the subs there, they can tell you who the builder is.Go to the permit office and tell them about your project.

Since it was so minor with no permits and would only take a few hours, I failed to get a contract signed or even ask about his insurance status or anything to that effect. 

I'd like to stop by more often but my schedule doesn't seem to permit it lately.  

First thing that comes to mind is whether the conversion was permitted...otherwise you cannot count the square footage (and room count) when you market the property. 

I assume then that this could primarily be a buy and hold or flip and sell opportunity, if permitted.

My company does energy efficiency upgrades for residential and commercial buildings and any time I need to pull permits (solar photovoltaic, for example), it takes at least 3-4 weeks for that permit compared to 1-2 weeks in my Los Angeles market.

Looking for contacts on who I can work with to put some permit plans together for a full 1000 sq ft basement remodel, only 500 sf of which is currently permitted (re-work ducts, electrical, minor plumbing for bathroom alteration, finishes, egress window etc...)  

If the zoning and covenants permit it, you may be able to find properties that can be converted easily.

Make sure that 2k includes leveling, skirting, utility hook ups, tounge removal (if needed), permits and porch/stair/landings.  

Thanks Rick,I was under the impression that the city might ask to tear down the addition if the proper permits were not pulled.