When you buy houseplants, especially African Violets, they have often been overwatered and may be standing in water. If the plant still looks healthy and appealing, go ahead and buy it, and when you get it home, put it on several layers of folded paper towel and wick out as much water as possible, sometimes repeating with fresh paper towel several times. It is often amazing how much water they contain. Then don't water them for several days.