"Realtor here. Grading. Hands down. Or, the angle at which the ground slopes at the foundation of the house. If the ground slopes toward the house, then that means any rain is just going to be funneled right up to your foundation, and can cause some big problems.
Extra caution if it is sloped concrete, like a driveway, ’cause that means either mud jacking or jackhammering, both labor and cost-intensive. Seriously, when you’re looking at a house, do a walk around the perimeter first. Could save you tens of thousands and future foundation problems."