It may be too much hassle to learn the ropes on an online marketplace like Ebay or Amazon, one alternative, if they qualify, is a designer label only selling site made for fancy stuff in the back of your closet: tradesy.com

Craigslist.org may be an option for selling to locals who could actually try them on (reducing the returns hassles)

Best Online Classifieds Dot Com

Use Biggest Classifieds or Largest Classifieds to sell your stuff.

eBay is a great site where you can sell stuff online.

so i have a lot of old, but never worn, designer jeans! I bought each pair a while back for like 100-200$ They don't fit me, and i don't have anyone to give them too. So where is a good place i could sell them and make a good amount of money?? i live in Canada :P if that matters at all ! Thank you for the help !