It's 2 a.m. and you have just found the perfect, most rare Louis Vuitton bag of this season on eBay. Best of all, it's about $300 less than you would have to shell out at the LV store in your local mall. Ladies and gentlemen, if it seems too good to be true it probably is. Before you hit "Bid Confirm" take a look at these tips for buying designer duds online without ending up with an overpriced knockoff.

First, check the sellers feedback! Look at every negative or neutral and beware of any that say "Item not as described." Reputable sellers of designer items usually have high feedback ratings and gurantee the authenticity of their products.

Second, don't expect to pay much less than you would pay in the retail store. In fact, expect to pay more for some rare items. For example, Hermes Birkin bags usually go for over retail value because they require an almost two-year waiting list in any Hermes store. Same goes for the Balenciaga motorcycle bag.

Third, you get the best value for your money in used items. Look for gently used or like new items from sellers looking to get rid of old designer items. I frequently sell designer shoes and handbags from my closet to make room for new arrivals (much to my husband's chagrin ... HA!). Insider tip: real Louis Vuitton bags age. The honey colored handles deepen to a medium brown with use. Look for this when buying used or vintage LV bags.

Finally, compare and contrast the photos from the auction to photos of the real deal. You can find pictures of anything online - check the reatilers's website for product info and close up shots of details. Also, beware of any item that uses celebrity pictures instead of pictures of the actual item.