My newsletter started as a hobby. It became a multimillion-dollar business.

CJ Gustafson turned his side hustle into a business. Courtesy of CJ Gustafson CJ Gustafson worked in finance for tech startups. During the pandemic, he started a Substack for CFOs. His income from writing and podcasting eclipsed his CFO salary. This as-told-to essay is based on a conversation with CJ Gustafson, founder of Mostly Metrics and CEO of Mostly Media. It has been edited for length and clarity. When I walk into a bakery, I'm not debating what kind of treat I want. Instead, I'm thin...