If you want to build a more sustainable web development business, find some larger corporate clients, and do basically the same thing but instead of the off-the-shelf theme, pay a designer $500-$1500 for a custom theme then charge $5-$10K per site. Get an intern or temp worker to do the data entry.
Also, I've found that "I want a website" type people really like to work on their own website once they have it. So don't be scared to let them have a go at the Wordpress (or whatever) backend. Just be ready to clearly explain the limitations when they inevitably make ridiculous requests.