It is possible that the condo's basement water leak stems from improper grading and drainage, and it may not be so obvious that you see the water enter and run across the floor. More likely, the water is running down the outside of the foundation, going under the floor and being drawn up through the force of capillarity. Most wet basements can be corrected through improvement in grading and drainage. See our wet basement section for more advice.
That being said, since this home has not been purchased yet, the basement water should be considered a major defect and should be corrected by the seller prior to closing. Because this is a condo, correction becomes a sticky situation. The seller may not be allowed to work on the exterior drainage as the land belongs to the condo association. You certainly want to avoid getting in the middle of that, too. Therefore, I'd get your attorney and real estate agent to work out the details of getting this condo's basement leak problem corrected before you buy the condo.