Any casual viewer of the BBC programme, Dragons Den will be aware of how easy it is for weaknesses or gaps to be identified. Depending upon the purpose of the plan, this may, or may not, prove to be critical. It is often easier to recognise such weaknesses and gaps, and be prepared to deal with them, either by noting them in the plan itself, or having appropriate answers available should the need arise.
You would first do a P&L for the present year for your existing business and the first year and as many years after as you would like to have your plan cover. Your existing business financials will be the foundation for building yourself a business plan for as many years out as you want. This data will tell you a number of things but first if you want to build your plan around what you want in life, you would need to decide some things about your life: 1. You would need to decide how much income you would like to have for yourself for each of the years you plan for. 2. You would need to determine what kind of profit margin you would want from your business for each of the years. 3. And by combining these 2 things into a P&L format you can develop a financial business plan that can extend as for into the future as you would like. 4. The first thing it will show you is how much sales you would need each year to give you the income and profit you would like. Once you see the sales needed, if you know your business well enough, you should be able to estimate those additional expenses needed to overcome capacity constraints that will occur as your business grows.