You could earn loads of money by being an SEO expert. And the 1st step to do to become an expert in SEO is by getting a certified expert, on this note I would suggest you take up the SEO course from Intellipaat to start your career as a certified professional. Then you could implement these strategies you learned and deploy into your website to get more SEO score overall and rank higher in SERP, and thereby increase the SEO score and gain more visibility in the search results.
Gaining more visibility means traffic to your website, blog, or any other content, etc.
Once your website or blog gets famous and you are able to clock higher rate of customers, then apply for monetization and then you could incorporate ads into your content, and with higher rate of traffic, more will be the conversion and thus more is the revenue generated. This is just one technique discussed here. At the end I would suggest you watch our YouTube tutorial on SEO to gain more insights.