I also think that one of the biggest issues is drainage. Having a house that has water problems is demoralizing and costly because you simply cannot fight it effectively without great cost. This isn't just water table or grade, it's also making sure the attic area has proper insulation, no heat infiltration from holes, attic access...etc, so that water dams can't form and have water leak inside.
This was a huge thing for me, the builder screwed up my grade and I had them come back in and put in additional draintile to pull water away from the house.
Do not take a single chance on water damage, none. It isn't worth it.