We've had two companies come to give quotes on the basement now, and generally positive news there - doesn't sound like the wall is actively damp and both companies sounded hopeful that the mold problem isn't widespread. Just overall hopeful that it will be a pretty quick and relatively inexpensive/painless fix.
One of the companies is a general contracting company and, on a whim, I asked if they also can fix dry rot. Our inspector noted some on an exterior window sill when we bought the house. This issue has been in the back of my mind since we moved in - one of those things that you're terrified to start getting fixed because it can suddenly become a much bigger issue/repair than you thought it would be, but you also know that by putting it off you're increasing the odds that it'll be a bigger repair. So figured while we had a company that could deal with this out, we may as well have them take a look.
The news on the rot was not good, unfortunately. Apparently the compromised part of the window on old windows like ours you can't just easily cut out and replace. Or if you tried to it'd be super expensive. They said we'll be spending about the same money to just replace the entire window. There's a beam above the window that he was particularly worried about because it has no protection from the elements but is a support beam for the house. So if that's gone bad it becomes a big job. Now, if we're very lucky, all we'll need to do is remove and replace the window (they might even be able to save the mahogany window trim). If they pull it out and discover the rot has spread, then we're likely to have asbestos in the walls and that becomes the nightmare increasing costs scenario. They won't even quote for the asbestos abatement because we can't predict yet if it'll be needed and cost would depend on the extent of the rot, so is highly unpredictable. So the whole thing is rather terrifying to think about. Silver lining is getting a couple new (less drafty) windows. And I'll have some peace of mind once it's done.
At least I've finished paying off student loans before we're doing all of this house work?