Okay this is easy all you have to do is to go to any pokemon center then once inside go to the second floor there will be a lady in the desk when you talk to her she will give you an item if you sell that item to a MART or market (POKEMON STORE) you will earn an easy 17000+ money P.S. it works anytime you want to do it! just remember to talk to the lady in the second floor of any pokemon center then sell the item to a MART