Ask HN: Successful one-person online businesses?

This question was asked 2 years ago (https://news.ycombinator.com/item?id=13326535) by mdoliwa, and I'm curious what it looks nowadays.

> How many people on hacker news are running successful online businesses on their own? What is your business and how did you get started?

> Defining successful as a profitable business which provides the majority of the owners income.