You can learn Carnatic music from the start on online. The sites are very useful for those who want to learn music. They have worked very hard and made this possible for us. Thanks to these great people.
Carnatic Music Basics, Geethams & Varnams Audio Lessons Archive
http://www.ecse.rpi.edu/Homepages/shivkuma/personal/music/varnams/
http://www.karnatik.com/
http://www.musicindiaonline.com/l/1/i/