Most courses have an option for paying in 3 or more installments. If you choose this option:
You get immediate access to the course when you complete the first payment.
The course remains permanently in your account after your payments are complete, and you can access it whenever you want to in the future.
If you cancel the payment plan before it is completed, you loose access to the course.
How to cancel a payment plan:
Enter the email you used to make your purchase.
Click the link in the email you received.
Click Payment Plans and choose "Cancel Payment Plan". If you're still in the first month/year of your plan, your subscription may appear under "Trials" instead of "Current".