Download WordPress and build something with it, on your own time. You'll spend your morning figuring out how to download everything and set up a development env

Download WordPress and build something with it, on your own time. You'll spend your morning figuring out how to download everything and set up a development environment, and your afternoon seeing how plugins and themes work. 24 hours invested in yourself and now you will know what the client is asking for when they ask about WordPress work. Your freelancing career will "happily decline" if you don't make self-education one of your priorities between jobs. All professionals have to work to keep their skills current -- teachers have to take classes regularly, plumbers have to learn about new materials and building codes, lawyers have to keep on top of new laws and decisions relevant to their specialty -- software developers are no different.