Ok, so that's a very broad stroke but it pays. If you are an expert in a field, usually people will pay good money for your counsel. If you haven't found your niche yet, a good way to start would be to upskill online. You can pick up a digital marketing course, learn the ins and outs of SEO marketing or even social media marketing, and then start small. You may not see money the next day, however, in the long run, it can become a good side business.