If you think about it, water should always be allowed to drain away from the foundation of a home on all sides.
Pooling water by, near, or under a home spells problems. You are looking at mildew, rot, insects, and foundation settling.
Walk around the home to make sure that there is nothing creating a dam or blocking the water from going AWAY from the home.
Jay had a large amount of good information to heed.
I would be very leary of this buildup and would be scepticle of the owners comment about the water sprinklers. Anyway, the sprinklers should not cause a back up under the home. If the homeowner is fudging here, where else could he be doing the same?
Have it inspected and make the owner pay for it and for you to see the original findings report. In the meantime, find a nother home.