I am planning on starting a website business and want to use WordPress multisite as my CMS. I will be creating hundreds of websites and need the ability to make them look very different and non-standard issue WordPress. From my understanding from browsing the WP Codex I will need to learn PHP, CSS, HTML, XML, JavaScript, JQuery, AJAX, and become familiar with the WordPress engine itself. Most of my customization of these websites will be purely theme based. I imagine I can start the business with a solid beginner/so-so intermediate knowledge of each language. It is just theme creation after all. All of the hard work is already done (WP Core) and XML/CSS/HTML is more about memorization than mastery.

My Question: Am I shooting too high here? Is my chance of success ridiculously small? I figure I have about one year to learn whatever I can before I have to start building my WordPress web development business. I have always been good at figuring out code I haven't studied but I don't know enough to write code from scratch. I am a quick learner and have a good 8 hours a day to dedicate to learning and practicing.

I would love to hear general feedback, suggestions, bad news, good news, anything you have to offer.