Sunfish - it depends what you are going to do and what category.
With the sort of stuff that I have got involved with the regulations start to apply shortly after the gleam in my eye. I'd need to do a draft certification plan etc. The bits of metal in the prototype for conformity inspection will need paperwork for when I get to that stage. Might be a new airplane or a major mod to existing one.
I'm sure that you can find aeronautical activities where there is minimal regulation. Perhaps you should read the Advisory Circulars that abound on the CASA website.