You can use all free software to get started like Google Docs, Grammarly for proofreading, other tools for freelancers, and start writing articles in Medium for practice.
Proofreading is polishing a submitted work before it publishes, including looking for spelling errors, grammatical errors, sentence structure, formatting, etc.
Much like freelance writing, editing, and proofreading, you can get paid for your design skills as a freelance designer.
You could choose to help people build apps, fix code on their small business website, or whatever you want really.