Answered by Adrian Ingram, e-book publisher & Youtuber
Personally, I publish kindle books so that would be my recommendation, though there are tons of different ways.
Anything using Amazon is probably one of the fastest and most passive ways in my opinion. If you have a skill and are okay with trading your time for money, you should be able to make $1200 a month offering your services on Upwork quite fast also.
Moreover, see another digital nomad's - Jacob's answer to a similar question.
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