"You know. A lot of major companies would charge you."
Um you would have a hard time proving that. Any one able to pull off something like that would have an incredible reputation already, and doesn't exist in the games industry. There may be apprentice, or intern type situations, but none of them work like that. There will always be payment for services rendered.
"Whoa Whoa Whoa! So your only in it for the money. Who said you were not getting paid for your hard work. But only if the game gets sold."
That's like a house builder telling his subcontractors they only get paid if the house sells.
Its called spec, or crowd sourcing, and isn't well tolerated anywhere.
http://www.nospec.com/articles/why-speculation-hurts