A good first step to earning money or building a career online is to assess your skills and passions in the real world. Do you enjoy taking photographs of landscapes? Do you have specific technical skills which could be beneficial to a particular group of people? Maybe you have web design skills, and would be well suited to getting information on the internet, or passing your skills on to others. There are a multitude of different interests and niches which you may already occupy.
Another good consideration to make at first is to assess where you would be best suited to begin a career online. Rome was not built in a day, and more than likely neither will a freelance writer's portfolio, a personal photographer's self promotion website, or an affiliate's sales funnel. If you are starting from the very bottom, then there is no shame in starting out your online ventures as small as possible and building up over time. This applies to anything, whether it is your portfolio of licensed photographs, or your portfolio of fiction/comedy skits which will hopefully be well received by an entertainment website.
Of the categories I have included, I would personally consider writing online to be the most convenient and simple of the options available to you. Although writing may not be everyone's strong suit or passion, it has the least amount of dependencies or requirements when it comes to getting started; you simply need to utilize a submissions page and get started. Next up would be affiliate marketing, as it can also be done absolutely remotely. Affiliate marketing has a lot of variety in its execution however, and setting up a scucessful sales funnel can take time and effort. Last up, I would consider photography to be the least convenient, as although you may be able to build your income from your photographs online, it naturally requires you to get out in the world. Of course however, those who are interested or passionate about photography would not likely be discouraged by this requirement.