It's a one-time payment. We don't have any catches or hidden fees.
Some of our deal partners that offer subscription services or plans with a set time length do require registration of a credit card or PayPal account when you sign up with them, even though you already paid us. Don't worry! You won't be charged again unless you continue to use their service past the subscription plan that you paid for up front, and you are free to cancel your service at any time before then to avoid incurring any renewal charges.