So, why not start out with what you would like to have in life for you and your family? Then develop a business plan that could show you exactly what your business would need to do to give you that life style. If you think about it, there is no other way where you have more control over what you want in life than letting your own business do it for you. If you work for someone else, you are sure not going to have as much control over your future.
The next thing to write (after the general description) should be your marketing strategy. For new or existing businesses, market analysis is an important basis for the marketing plan and will help justify the sales forecast. Existing businesses will rely heavily on past performance as an indicator of the future.