​I’m a coder. What are some practical, low-cost business Ideas I can start solo?

I’m a solo developer with decent coding skills (web dev, automation, scripting). I’m not looking for the next billion-dollar startup, just something that I can build myself, get users, and possibly monetize.

Requirements:
– Low to zero startup capital
– Can be done solo or with minimal help
– Something people are willing to pay for

Open to ideas like SaaS, tools, B2B scripts, niche marketplaces, or anything that solves a real problem.