If so, it has WAY too many red flags and you’d literally have to tear it down and start over to get it conforming.

Land value, less tear-down cost, less the bargain discount you'd like! 

Selling a piece of land with utilities to the site, zoning use approved, scraped and cleared land, etc. is very different then selling a piece of land with an old house on it for a tear down and lot had to be cleared and graded.As a commercial developer if a seller wants a quick sale then it will be a low cash offer.

Eventually we had to tear out most of what we put in there.

I've even moved all hist stuff out of the area, and barricaded that unused entry way (plywood and nails), and posted no trespassing signs, only to have him tear it all down and move back in before the next morning.My biz partner gave the police an earful, and they said they'd patrol the area more frequently (stop by whenever they're around), but I'm not too confident that anything will be done.So, I'm brainstorming for some options.

These properties can make you a lot of money, but unless you know what you are doing, they will tear you apart. 

Also, gas and vehicle wear & tear, marketing expenses, never mind whatever their broker split is, or any other fees their broker is charging them.

So maybe adding a ramp access outside is readily achievable so you'd want to do that, but completely tearing apart an existing bathroom to create the necessary space is not readily achievable; 2) is the property in a historic district?

The RE broker found someone reputable and got back to me with a quote of $45K for the big office building and 40K for the smaller office building (would need to be done in next 3 years) – this would include tear down, using shingles that last 30 years, repairing mortar joints on chimney, etc.

Like wear and tear on carpet?