With online classes, there are numerous methods to make money.
You can set them up as a paid email course, on your own website, or on a specific website that advertises courses like Udemy. You can profit directly from a course or indirectly by selling the course's materials (or both).
With a paid course, you can immediately make money. There are other websites that offer courses, like Fedora and Udemy. There are numerous resources available to you if you search for "sell your course online." AWeber, InstaMember, or even just a PayPal button on a website that requires a login can be used to set up your course on your own website.
A free course can still be profitable for you. You may use the course to grow your email list by offering your audience a brief free course via email or in a membership on your website. Then, using the course and the email list, you may advertise more products to them. You could, for instance, include a link to your premium courses in every email you send out about the course.
Keep in mind that you can include recommended items that match things your audience will need if they want to succeed at whatever you are advertising through your course on any page on your website (such as the page where people go to grab the next free module of your course).
If you want to, you can make money using all three strategies. You can still add supplemental products to the delivery page or via an email newsletter that the students sign up to receive whether or not a paid course is delivered.
A series of courses are an excellent way to earn more money through online courses. This works very well if the first course is free, then to learn more they have to pay for the upgraded future course.
You can always make money with courses. You just have to think about what your audience needs outside of the course, and you can promote those things to them as well. You can make money from the course directly, and then make money indirectly by promoting complementary products, services and more courses.