At the rate of $100 per day, assuming a normal 40-hour / 5-day work week, you would have approximately $2000 per month in income. After taxes, this is still enough to live on for a basic existence in many parts of the US, as long as you stay out of major cities and metropolitan areas.
This is more than possible given some skill, talent, a work ethic, and an Internet connection. Your chief venues will be the freelance and gig economy. For freelancing online, you will usually want to start with UpWork, which is pretty much the only option currently. Later you can develop your own leads and cold-pitch clients on your own, but right now you need to get experience.
Here are your career options, assuming no education beyond high school and self-learning applied for free through the Internet.
Writing, editing, and translation
The whole Internet is made largely from the text. The opportunities for a writer, editor, or translator are endless: blogs, ad copy, social media marketing, scripting for YouTube videos, eBook writing for hire, fan fiction, erotica, translation, product descriptions, forum moderation, white papers, grants, atmospheric text for video games, press releases, and more. The web is largely a text-based medium, and the whole world uses it.
You need some very well-honed skills in various applications, and the freelance graphic design gig is a bit more feast-or-famine, but you can certainly average $100 per day. You’ll find the most work in logo design, ad design, website graphics, icons, and illustration. If you have a hand in 3D rendering, video game graphic design alone can be a very lucrative profession.
Uber and Lyft
Switching to the more physical realm, the old taxi industry is being taken over by gig workers. Anybody with a car and a phone can become a ride for hire. You have to factor in cost of gas, vehicle maintenance, and other factors, but gig drivers in major cities can more than clear that and make a living too. There’s also a sub-market for cargo transportation, typically food and store delivery on a freelance basis.