My first home was a century old fixer-upper with stone foundations. I never found a way to seal a stone foundation, so all the drainage improvements depended on what could be done outside to the grade and downspouts. The celler was always somewhat damp because ventilation was not a real big item in the late 1800s.
Find an excuse to take another look at the place and see if the wet locations correspond to grade or downspout / gutter issues. If so, the fix could be fairly inexpensive, or a negotiable part of the deal.