Your Own Idea
Ideas can appear out of nowhere and it is often said that the simplest ideas are the best ideas.
That said researching thoroughly your idea is a crucial key stage in its development to reality. Mistakes can be time-consuming and expensive.
Assessing the market, if there is any competition, if so who it is as well as developing an original take on the idea/product are key components of your business plan. There are many more. However, being honest with yourself and being brave to ditch an idea is nothing to be ashamed of.
Make your business plan as detailed but as concise and clear as possible. Include financials and your short, medium and long term goals. This will be your reference document as you start and run your business. Do not be afraid to change your plan as you react and adapt to market conditions and client demand and feedback.