Anything related to web-design should be a side-effect of the true product you're selling, which in your case should be web-based software application development (IMO).
My opinion:
#1) Get really good at a web-framework. Doesn't matter which, but something like laravel would be a great choice. Learn MySql/MSSQL to go with it.
#2) Market yourself as a specialized consultant and bill $100 hr+. I don't know what market you're in, but if this is a big leap for you then work up to it. The kind of clients you want to work with will pay this without blinking. Sometimes they won't even know about the bill because it goes straight to AP. blah blah blah patio11.
#3) Never say you do web-design. Say, 'I convert your MS Access application that runs a critical component of your business (barely) into a multi-user/role, always-online, accessible-from-home web-application. Along the way we're also going to streamline this to make your company more money. It will pay for itself. That will be $30k.'