Avoid surprises by understanding the rules for third-party sellers on these sites. By Andrea Browne Taylor, Online Editor November 4, 2015 Convenience is one of the biggest draws for online shoppers. Just a few clicks on your computer or smartphone, and your order will be delivered to your doorstep, often in just a day or two. But shopping online isn’t always the same as shopping in a store, especially when you’re dealing with Web sites such as Etsy and Amazon that allow third-party sellers.See Also: Worst Things to Buy on Amazon.com Here are three things you should know before buying from third-party sellers on either one of the popular e-commerce sites. Shipping isn't always free One of the biggest draws of Amazon’s $99-per-year Prime membership is the free two-day shipping on purchases. However, only items that are sold by Amazon, as well as many items that are fulfilled by Amazon, are eligible for that option. Products sold and fulfilled by third-party sellers on Amazon.com don’t qualify for Prime shipping. Ineligible products should display a message that says “Not eligible for Amazon Prime.” Refund and return policies vary When dealing with major retailers, there's comfort in knowing that if you don’t like a purchase, you can always exchange it or get a refund. That’s not always the case when you buy an item online through a third-party seller. On both Amazon and Etsy, third-party sellers set their own return, refund and exchange policies. It’s important to read a seller’s return policy in its entirety before making a purchase. Advertisement Disputes can be harder to resolve Keep in mind that neither Amazon nor Etsy has direct access to order information for transactions sold and fulfilled by third-party sellers. As a result, they encourage customers to work through any issues directly with the seller before they’ll step in. Be sure to document any correspondence you may have with the third-party seller just in case you have to escalate the situation to customer service at Amazon or Etsy. Learn even more things you need to know before buying from third-party sellers on Etsy and Amazon.