Another consideration. Should the business plan be a document that is focused on selling an idea for a product or service? For many years I worked in a company that did not want anything in a business plan that could be construed as showing a bias towards or against a project. The mantra was to only present facts in the business plan. The Operations Research Department was there to review the analysis as being unbiased. To handle the "what if" scenarios or sensitivity analysis we prepared a supplemental analysis documents which were mostly financial oriented. Personally, I like a factual approach and use the presentation of the final document to point out the conservative aspects of the content.
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're sure not going to have as much control over your future. So how would you go about making a plan like this? Well if you know a fair amount about business, you can. It will take some special calculations and some work but if you know how to put together a Profit & Loss Statement, you can probably do it.