A good sign is when you can look at a website you have never seen before and quickly spot what is holding it back. If you understand why pages rank, how to fix technical problems, and how to write content that brings in traffic, you are already ahead of most people. You do not need to know everything before you start charging. If you have gotten real results, even for your own website, that is enough proof to begin. What do you think is the clearest sign that someone is ready to charge for SEO work?