This reminds me of the Home Depot and probably others scam where they offer you a no interest type deal if you get a card for your first purchase. Usually people do this for a large purchase like a riding mower or some big purchase. Well when they go to use that card again the purchase is charged interest and the catch is your payments are credited to the oldest charge first. In this situation you are paying off the no interest charge while the interest bearing charges are sitting their accruing interest every month until your non interst charge is paid off.