STEP 1 - company is already established
Let's look at this the other way round ....
I have, say, £1 million to start up my own flight school. I buy a few decent aircraft, invest in the costs of setting up a TRTO, maybe an AOC as well, rent a hangar with offices, and employ staff.
My new flight school is making a modest profit; enough to pay instructors and keep a roof over my head.
Now Paragon2, give me one good reason why I should want to sell you a 20% stake in my business (which I value at £200,000) and give you training at cost? Is there really that much a shortage of instructors that I need to sell part of my business to get one?
It doesn't make business sense and I'm afraid, if you don't even know that there are tax and stamp duty implications let alone the difference between a partnership and a limited company, then you shouldn't even be contemplating it.
Cheers
Whirls