Plugin to create restricted / paid environment

Hello everyone,

I was wondering if there was a plugin available in order to setup a paid environment, where my users can access certain restricted content by paying a small fee.

The idea is as follows: I have training courses on video and i would like to offer those videos to my users in return for a small amount of fee. The ideal situation would be when people could checkout per training course that they would like to watch.

So does anyone know if there is some kind of plugin available to create some function like the above?
Thanks a lot in advance,
Robbert