I actually had him place two offers for me but on one of them the owners decided to demo their home and the other one was already sold.

Come to find out most of the demo and construction has already been done.  

Hi Larry, if you are not doing the work yourself, my suggestion would be to contact a local mold remediation company and have a conversation sending the pictures to them, most investors just hire demo crews with proper gear to do the work and use the mold remediation estimate as a negotiation price point. 

What I am talking about is the 10,000 houses there that are on the city's demo list.

There is another offer that went stale from COVID that was in the "mid-300s".When I walked the property, I noticed a number of issues with the property that would come up at inspection at which time I would ask for a price deduct; I estimated this around $27k (needs boiler, new electric service, old foundation that needs demo, underground oil tank...)Should I consider those deduction in my initial offer or should I wait until we are under contract and allow the inspection report to bring them up?

A contractor I use was telling me about an electrical job he did where he bid to demo all knob and tube and run new electric on a high end flip.

You should also be able to ask for a mini demo and have them work through a few accounting tasks so you can see the similarities or differences.

Removed walls in living room to make it more open concept ~$2.5k (we did demo)4.

After closing there was two weeks of demo and then a planned quick turnover for another place.  

You could find somebody pretty cheap to demo it in 1-2 days (not that much money); than you could put down whatever you wish.