Depends on how much you want to get for it and how quickly you want to move it. Some shops pay cash, but a lot only do store credit. If you aren't in a hurry, www.tcgplayer.com is the eBay of Magic cards. If you just want to get rid of it, try Facebook's online yardsale in your area or look and see if there's a local Facebook group for Magic players. They usually know who the collection buyers are.