To perform this glitch just go to a store and purchase an item. Then go to the 'Sell' option and hold RT and keep selling the item. If you do not release RT you will keep aquiring coins until you do release it at which point the item is sold.
Just a note before we start you have to do this without the recent update. When you goto sell a weapon or a piece of armor hold the RT button (right Trigger) and raidly press the A button and hey presto. When you let go of the RT button you will sell the original item but you can just buy it back from the shop ;-). Be warned it only works with weapons and armor not you cosumables and other items Including arrows.