I read just far enough to know your argument was going to be "free will to decide what contract to sign".
Except that entire line of thinking can be destroyed with a single observation.
contracts freely signed can and are deemed invalid if they're too onerous. Boom. Your entire argument falls apart.
Allowing a 17-18 year old to sign away their labor for longer than they've currently been alive is called ownership. We do this with corporations in the form of stocks. WE DO NOT DO THIS WITH PEOPLE.
There are things in this world that we as a society do not fucking do, and selling ownership to young adults is one of them.
You're completely ignorant of people and the world. completely. The first thing these companies will start doing is trying to protect their investment, only because it's a human being involved it's going to start turning into control and oversight.
that's fucking slavery.