Like Robo said, you can use them immediately, but there's a bit of a catch in the payment plan. You need to pay the down payment, which is the cost of a 1 day ticket, then the remainder is divided into *12* monthly payments, and the first of the monthly payments is taken on the same day that you sign up for the plan. We had a few friends who were prepared for the downpayment amount, but didn't realize that the first installment was also going to come out that day. (It's taken as a seperate charge, though, and you can use a different card for the down payment and the monthly payments if you want)