You may (and usually should) invite students well before you think your courses is ready. For example if you still working on some topic and don't want students to see it yet, simply flick "published/unpublished" switch. When topic is unpublished - students don't see it.
The only limitation on edits we have is for quizzes. If at least one person submitted the quiz - you can only modify typos in questions, but can't add any additional questions. Thus, we also recommend to keep quiz "unpublished" until it is absolutely ready.