Make sure the garment is sturdy - tug on the fabric, zippers, and seams. Wash them several times. Vintage clothes stink and the smell only gets worse with body heat. They can be a good source for patterns, accessories, and magazines, though. The Atomic Garage in Valley Junction has some 40s-50s clothes, as well.
Women can find dresses, though they tend to be of poor quality and high price.
Des Moines is surrounded by larger cities with good antique and vintage stores. Try Minneapolis, Chicago, Omaha, and Iowa City. We usually have good luck at vintage stores in Chicago and Omaha. She can also make bloomers and skirts. Customers are always welcome to provide a pattern, as well.