...I am having a demolition guy coming out to estimate tearing it down and hauling away debris. So that figure will give me a base figure for reducing purchase offer by some minimum amount..... quote]
I'm not in a position to do so but if you made me that offer I'd show you back to the road back to where you came from.
If it was a dangerous or junk building I'd clean it up before offering for sale but I'd not tear something down at my own expense for a buyer.
You might be able to get insurance, like title insurance, that would pay if there are code issues found post sale. MikeD74T