Highlight the number of stock you have for the AK-47 and delete that number to leave it blank. After that, move your pointer over the number of guns you want to buy or sell and select any number. Then click "Sell" repeatedly and watch your cash level rise. Your cash level rises because when you deleted the number of stock, the game does not know how many guns of that type you have. Note: This only works with AK-47s.