It may be easier than you think to figure this out. You would do some research and with the aid of the U.S. Census Bureau you can roughly determine whether your plan can be supported by your market or not. So what do you think? Is it better to build a business plan around what you want in life then see how your business can maybe give you that or is it better to use a sample business plan for a small business where you are probably guessing?
A plan like this would show you how much sales your business would need to do, what your fixed and variable expenses would be, what your material cost, labor cost and profit would need to be to provide the income and profit margin you want. You can see pretty quickly if it's possible for you to get your business to that level. I don't know of any better way than to have your business give you the income and profit you want. What's neat is you can determine what you want your income to be and your profit to be over the next few years and develop a plan that can show you exactly what your business would need to do to give you that income and profit. And with just a little more data you can actually determine how many customers you would need for each year you plan for and how many leads you would need. From that you can actually determine what size market you would need and whether your market is big enough to supply those leads that could be converted into customers.