(holy crap, why didn't someone warn me about the start-up costs!?).
What kind of startup costs?
Time, so much time. I'm a lab and lecture type of guy. In a normal class, my PowerPoint slides consist of pictures, graphs and tables, very little text; and then I talk and ask the students questions, and talk some more. I like to talk with chalk in my hand too and I use the black board a lot. None of that translates very well to an online version of the class. I've been adding recorded narrative to PowerPoint slides, making podcasts, adding (and finding) video clips, developing online quizzes and tests, adding a lot of text to slides, learning a entirely new way to teach, and on and on.
The "online classes" section of this forum has been very helpful. I've been lurking there all winter.