Hey.. It's good to know that you have been thinking about your career in Big Data. There are many companies that hire freshers to work on Big Data. And the basic knowledge you'd require is basics of Core Java , basics of MySql and basic *nix commands. If you know these, then you are ready to start in Big Data. But if you think you are not ready, then you can work elsewhere, have an experience of 1-2 years, get certified in Hadoop courses and then switch to Big Data.
To know more about Big Data, It's recommended to join Data Architect Certification today.