I was successful with a side project, but it was to solve a problem my employer had. I kept it closed source and provided it on my own site for free, and it was

I was successful with a side project, but it was to solve a problem my employer had. I kept it closed source and provided it on my own site for free, and it was clear it was mine, not theirs. Having dealt with problems and additional requirements, when I left I launched it separately as a paid Service with a free tier. Proved to be an earner over many years. If you are employed it might be a path to consider?