A fitness site can have numerous revenue streams. Create healthy eating plans and recipes and lock them away as premium content. Promote and sell a fitness training course, eBook, or a series of videos. Or advertise your own personal fitness services on your site. Topfithub is a good example of a fitness site with decent video content alongside product reviews.
Offering specific online SEO services is also another online freelancer role that businesses are crying out for. If you know how to improve a website’s SEO by doing keyword research, creating content that can rank in search engines, adding metadata / schema to posts and pages, and building backlinks to a domain, to name a few tasks, then this could be a great line of work for you.
Next, you’ll want to pick a WordPress theme from somewhere like ThemeForest, Elegant Themes or OptimizePress. This is the barebones design of your site, which you can then customize with your own branding, copy, and images. That being said, you don’t want to cheap out. It costs less than $100 to buy a theme that will make your website look professional (and you can upgrade to a completely custom design once you get the business going).
One of the cool things about Google AdSense is that it's so easy to get set up. If you have a blog or website, you can sign up for a free Google AdSense Account. From there, Google will give you a unique code that you will paste onto your website. Google takes it from there, tracking your page views, traffic, and earnings on your behalf. There is no upkeep or maintenance to get this thing going, which makes it a no-brainer if you have a website already.