Basement walls look bad!

I would say that with an investment of that size, you should definitely get a professional if you have no idea yourself.

What would certainly help a lot is regular ventilation of the cellar so that the moisture can escape.

A few years ago, I bought a sandstone house from 1692. The cellars were all damp there as well. Then a forced ventilation system was installed. It took about a year, then they were almost dry.

However, the sandstones are not plastered and therefore release moisture well.

I would also consult an expert. It worked great for us too. They were able to give us many tips and you will sleep better afterwards.

Professionally identified defects also provide good material for price negotiations. Apart from that, they protect against ruinous gut decisions.

The damp walls would still be one thing, but what worries me much more are the many dehumidifiers. Why does the current owner have so many of those things in the basement, is he trying to cover something up for the sale? And what is the condition when the dehumidifiers are no longer running, a natural pool in the basement? Tell your son he is an idiot if he doesn’t want to spend the money on the expert. In the end, the problem is much worse than expected and the solution to the problem is not something that can be done quickly because of everything going on around the house.

That is completely normal in old buildings. As long as it is not going to be living space, it is also not a problem. If you want to upgrade it a bit, a lime plaster and lime paint are recommended. This allows moisture to escape and prevents mold from forming.