You don't need to have any backlink before you get approved for google AdSense. How ever, the following are few things to consider before applying for google Adsense.
you should publish ten articles
The articles should be informative, educative and valuable to your readers
Your website should be friendly and easy to navigate
You should also have the legal pages like privacy policy, disclaimer, and terms and condition pages.
Then your traffic source should be real visitors and not some sort of robbort