What are the benefits of a Business Plan?

Benefits of a Business Plan include:

Ensures you take a disciplined approach to analyze your business ideas.
Shows your investors and lenders that you have systematically analyzed your business ideas.
Helps you clearly define your goals and what you want to accomplish.
Helps you identify and analyze your risks as well as your opportunities.
Helps you assess the strength of your target market.
Helps you define your day-to-day business processes and challenges.
Helps you analyze costs and capital requirements.

Here's what should be in your business plan:
Title page. Start with a name the name of your business, which is harder than it sounds. This article can help you avoid common mistakes when picking.
Executive summary. This is a high-level summary of what the plan includes, often touching on the company description, the problem the business is solving, the solution and why now. (Here’s what you should include in the summary and how you can make it appeal to investors.)
Business description. What kind of business do you want to start? What does your industry look like? What will it look like in the future?
Market strategies. What is your target market, and how can you best sell to that market?
Competitive analysis. What are the strengths and weakness of your competitors? How will you beat them?
Design and development plan. What is your product or service and how will it develop? Then, create a budget for that product or service.
Operations and management plan. How does the business function on a daily basis?
Finance Factors. Where is the money coming from? When? How? What sort of projections should you create and what should you take into consideration?
For each question, you can spend between one to three pages. Keep in mind, the business plan is a living, breathing document and as time goes on and your business matures, you will be updating it.

Evaluate yourself.
Let's start with, Why do you want to start a business?

Use this question to guide what kind of business you want to start. If you want extra money, maybe you should start a small business of your own If you want more freedom, maybe it's time to leave your 9-to-5 job and start something you have wanted to do and think you can earn too.
After you have given a lot of thought and have arrived at the reason, start asking yourself even more questions to help you figure out the logistics of a business you start, and if you have what it takes to make it real and profitable.

What skills do you have?
Where does your passion lie?
Where is your area of expertise?
How much can you afford to spend, knowing that most businesses fail?
How much capital do you need?
What sort of lifestyle do you want to live?
Are you even ready to be in business?
Be 100 percent honest with your answers. This will create a foundation for everything you do in your life from this point forward, so it's better to know now than rather than later.

Do market research.
Is anyone else already doing what you want to start doing? If not, is there a good reason why?
Start researching your potential rivals or partners within the market. You break down the objectives you need to complete with your research and the methods you can use to do just that. For a long time, I conducted interviews than in the old days by telephone. Now online or face to face. You can also offer surveys or questionnaires that ask questions like “What factors do you consider when purchasing this product or service?” and “What areas would you suggest for improvement?”
The most common mistakes people make when starting their market research:
Using only secondary research.
Using only online resources.
Surveying only the people you know.

Many businesses and industries do things one way because that's the way they've always been done. In those cases, a fresh set of eyes from a new perspective can make all the difference.
Use the better, cheaper, faster approach. Do you have a business idea that isn’t completely new? If so, think about the current offerings and focus on how you can create something better, cheaper or faster.