A plan is not etched in stone. It is subject to change. As time goes on, things change in this world and businesses like everyone else are subject to change. A good plan will reflect changes that a company has to make to keep it competitive and successful. Where can you find samples of a business plan for a small business? If you go into any of the search engines such as Google or Bing and type in "samples of a business plans for a small business" you will find websites with this information. This is why it is important that a small business should have a business plan. If you look at those small businesses that are successful, you will find that most of them all started with and have a plan for their business.
I have written business plans for all manner of industries: a coin operated jukebox company, airlines, travel companies, new product launches, and anti_aging product companies. It is not necessary to have a passion for the product or the company to write or develop a business plan. What you must have is a passion for aggregating information, getting involved with and understanding the service or product, and understanding the financials of the product or service. By financials I am not referring to having a CPA before you undertake the task, but rather understanding the presentation of the information and analysis/ numbers to support the activity being planned. Financials are important because they are the score card in the world of commerce.