Adobe has introduced subscriptions to their Creative Suites programs, allowing you to pay on a monthly or yearly basis. This could be a convenient option for someone working on a short term project. Subscriptions include updates to future releases, as well as online support should you need it.
“Adobe® Creative Suite® software offers multiple options to help you get exactly the tools you need. Now with the convenient new subscription option, you can have the latest features and functionality of Creative Suite for a low monthly cost.” -Service Description
Link: CS Suites Subscriptions