Its best to see a house when or right after it rains. Fortunately in Pittsburgh that's most days. Always check the basement for smell and touch the walls, some owners just put new paint in the basement rather than Drylock, it will have a different feel. Look at the floor joists overhead for mold, most people forget about that when they are cleaning up the basement for sale. Always look at the bottom of items in the basement, water heater, stair landing, any posts etc.