Hi,Chris.
         Having been a registered Builder for 30 yrs. I would only be an owner builder if you have had previous experience with building and contracts etc. and have enough time to supervise and coordinate the works.  Some of the larger volume builders who build in a particular style that would  fit  with your dream home would be my choice. This can be with a fixed price contract and  with a guaranteed completion date. Smaller projects could then be undertaken such as landscaping etc. by yourself.  A lot of people can get into trouble when they split contracts as no one is accountable with warranty insurance. I have just priced a two story  home with a volume builder to work out the figures on a project and they can build for less than I can even discounting my own  time. A contingency sum of 10 %  should be allowed for.  I hope this is of some help.