This is only my opinion, others may disagree, but it works for me.
Forget the business plan, you can get started for £1000 which can be put on your credit card.
Buy a machine , practice with your own carpets, ask loads of question here, as to what chemicals to use, and all that.
Bang out your advertising, take the calls, do the jobs, and you should be in profit.
A business plane if done correctly will take weeks to do. By this I mean every figure validated. A plane that is put together with guess work and assumptions, is like peeing in the wind.
I started carpet cleaning with a £1000 machine, 30,000 flyers and at my heights were booking over 500 jobs a week, we have done over 300,000 clients since. But like I said it worked for me. But maybe that's because I am an aim fire person. Some are ready steady aim aim fire people, and they still don't hit the target. Some don't even get off the ground. There is a great book, you can buy it eBay, it's buy a man named Fred Deluca, it's an easy read, after readying it you will be so fired up, I'm sure you will put your heart and soul into it.
But if you must write a plan. Use business plan pro. I did one to get my green card back in 2006, and it took me 13 weeks to write. But every figure was validated. So when I went for my immigration interview, everything stacked up.
Have fun in the world of carpet cleaning.