I work at the Fortune 200 during the day and freelance at night for small/medium merchants that need occasional support from a Development and DevOps point of view.
I started with Magento 1 in 2009 right out of college by owning an import/export ecommerce store. After the first year I sold the company and decided to code full time.
Today I work for a Fortune 200 merchant and freelance nights and weekends for small to medium merchants that need development work but cant afford a full-time developer.
I limit myself to 3 freelance clients at any time. During the onboarding process for a client, I review their current code and server environment and come up with an action plan of how stable the codebase is as well as how secure it is. At the end of the day, every client I work with expects me to own their code and be able to make quick decisions to ensure reliability.