You can buy Lightroom CC with an Annual plan.*(Lightroom and Photoshop | Adobe Creative Cloud Photography plan )
Or if you haven't used it before you can try Lightroom for 30 days Digital photography software | Download free Adobe Photoshop Lightroom CC trial
Lightroom 6 is also available as a Standalone Product. Refer this link Products
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To get a better answer, you need to be a bit more verbose about what you are thinking about.
To answer the question as asked, when you stop paying in the subscription license, the Develop module will stop working. You will be able to view your images and export your images, but you will not be able to edit any new or old images.