I have come across some great online platforms where you can purchase a yoga or exercise course for very little investment. I use two platforms, the first is the https://www.dailyom.com/ where i have tried several of Sadie Nandini courses . If your new to yoga choose a beginners level course .
https://secure.dailyom.com/cgi-bin/courses/displaycourse.cgi?cid=167&aff=0
Yoga International offers a wide range of yoga courses for all levels and all styles