That's a complicated answer as it comes down to a few factors. Being frugal and saving before I decided to quit working, changing my spending habits drastically to allow myself to save even more money, publishing an e-book and working jobs on the side, having some income from a former job, as well as planning my travels well in advance for the cheapest costs. And now I work through my blog and my YouTube channel, which doesn't earn me so much money at the moment but in 10 years or so I'll be good to go! (I'm a super long-term planner...haha) All of these allow me to live simply as I travel. I live on much less money now than I used to when I was working properly, but life is more enjoyable now that I have the freedom to work remotely. I hope that answers your question somewhat!

Other nomads find other ways to sustain their travel lifestyle. Teaching English in a foreign country is a good idea as you're paid and have a regular job while living abroad. Several of my friends did (and are still doing) this to fund their travels. Some people are lucky enough to have jobs which allow them to work remotely. Everyone's situation is different but planning well in advance and living simply are key. The more time you have to plan for your travels, the better. :)