LightCMS is the fastest growing white-label Content Management System on the market. Their Developer Program gives you all the tools you’ll need to build your web design business on a top-tier, cloud-based platform and your customers don’t ever have to know it’s not your CMS. They’ll even invoice your customers on your behalf. You’ll of course have full access to the HTML and CSS of your sites and you’ll even get a free website for your business.
If you're sick of patch updates and security vulnerabilities, LightCMS may be a good option. You can try it free for 14 days. No credit card required.