Buying goods and reselling them for a higher price is at the core of any retail sales business model. But knowing how much to mark up, or increase the price of goods for resale, can be a challenge.

Long before "I Can Get For You Wholesale" was a hit Broadway play, consumers have been trying to figure out and retailers have been trying to keep quiet about what they really pay for goods they sell.

Opinions expressed by Entrepreneur contributors are their own. In Start Your Own Retail Business and More, the staff of Entrepreneur Media, Inc. and writer Ciree Linsenman explain how you can get ...