There had been a "smelter" in the area in the 1800's and some properties had shown high lead content in the soil.

One thing that can help you determine what you're getting into is having a core sample taken of the property. it will tell you soil type, groundwater and rock depth. if some rocks are big enough you might need controlled blasting. if your basement is below the stream bed grade wise, you would likely have to be pumping water 24/7 during the construction part. im not sure how well a poured concrete wall with the waterproofing on the outside will stand up to the water, but of course it would be better than a block basement. builders would reccomend under drains to drain the water. the best way to do this is mechanically, without a pump or you could still wind up pumping water 24/7 after construction is complete.

@Sandy Paris @Jenkins Ramon Thank you for the kind words

Lots of broken windows and soiled floors, and likely structural/foundation issues as it was built in the 1920's.

Would submitting an offer contingent on determination of suitability to build by the county (soil samples, utilities/infrastructure improvement costs, design approval/permitting, etc) be considered common and reasonable for a vacant lot purchase?

Most likely the buyer will not be paying it, the lender will be crediting the buyer usually or suffer a soiled reputation for over promising and under delivering.

Just make sure you have something in there that says that the owner will remove (not just decommission but removr) any discovered inactive underground storage tank and remediate any contaminated soil if found.

Here are some things that a buyer may need to know about the property, besides liens and comps (comparable sold properties): zoning, setbacks, easements, utility length/connection cost, phase 1/2 soil assessment, survey, legal access, and flood zone.

Some soil testing has been completed.

.: This is not legal advice, but I would be tempted to tell them to pound sand. I