sugarcayne on "How do you insert a video that people have to pay for with paypal before viewing"

Hi,
I want to insert a learning video where people have to first pay for the video before they can see it? Im not sure if this is easy to do or even what this is called or how it is done...I see them online all the time for guitar lessons and things like that.
does anyone know what this is and how to do it?
Thanks! Sugarcayne