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.
New businesses have a greater challenge - they will rely more on market research using libraries, trade associations, government statistics, surveys, competitor observations, etc. In all cases, make sure your market analysis is relevant to establishing the viability of your new business and the reasonableness of the sales forecast.