Owner of FunnelXpert. Passionate about helping new bloggers make money selling digital products.
I took my blog FunnelXpert from zero to a point where it makes money on a regular basis using SEO.
You don't need an expensive platform to sell your courses, however you do need an online platform, otherwise you are missing out. I built my own online courses and I explain in detail how this can be done without a huge investment: https://funnelxpert.com/online-course-plugin-wordpress/
I use WooCommerce and PayPal, neither of these requires any investment. The plugin that I used for building my course costs $218 and it includes lots of additional features, such as lead generation, landing pages, etc.
Offering a small section of your course for free helps you get leads.