What is best way to sell units of courses?

I have a course that I am setting up. It has 10 units in it. Each Unit could also be a standalone product and I would like to be able to sell them individually. What is the best way to accomplish this? Do I need to create 1 Course for each Unit and then 1 big Course with all the Units together? Or is there a better way?

For example, I would sell each unit for sometime like $20 and then all units rolled up for $150.