The various plans are listed on the Creative Cloud Plans page at https://creative.adobe.com/plans. You have a few options. First you can do a 30 day free trial. After that you can sign up for the month-to-month price without signing up for an annual contract. If you sign up for an annual contract then you will be not be able to switch to another annual contract without cancelling it and paying a penalty fee. Since you own CS5 Master Collection you could sign up for the Upgrade individual annual plan. This is what the individual student plan normally costs, but currently there is a special that will end on April 5th.
The Creative Cloud FAQ here https://www.adobe.com/products/creativecloud/faq.html covers this and more.