Yah, better get your pocketbook out! Knife-Edge has been saying that they're almost ready to release the utility that allows you to create custom aircraft. But it hasn't come out yet. So unless you shell out extra cash to purchase Add-ons #1-5, your stuck with just different sizes, colors, and minor modifications of your existing aircraft.
Like you, the impression I got was that I would be able to freely download all kinds of planes and heli's off the internet. I was a little disappointed.
Now don't get me wrong, I love the G3 sim to pieces! I have purchased one of the add-ons. I don't remember if it was #4 or #5. It was the one with the KingCat, Osprey, and Tigermoth.