Also unless someone or something manage to unseal Kyuubi, he is looking down on a road where he will die together with Naruto. It has been said that if Naruto dies, Kyuubi dies. And if he don't get unsealed Naruto will eventually die from old age. So Kyuubi can either try and fight Naruto, or he can join him. If you where Kyuubi, wouldn't you rather make a journey together with Naruto rather then just be a passenger, not having anything to say about anything? Not to speak of the fact that it should get lonely not having anyone to talk to for a hundred years (your last 100 years unless you manage to get unsealed).

And i don't see it as Kyuubi becoming Naruto's bitch just because he starts to help out, but more like a partnership. Because that is what Killerbee and 8-tail's relationship looked like to me. Didn't feel like 8-tail's was a slave under Killerbee.

And the fact is Naruto has never even tried to be friends with Kyuubi. When they met for the first time, when Jirayia threw Naruto down that abyss, Naruto demanded that he got access to Kyuubis chakara as rent for being in his body. And Kyuubi in return only gave Naruto access to it because if Naruto died, he would die. And no encounter so far has been one where Naruto has even tried to reason with the fox at all. It has all been either Naruto demanding things or Kyuubi trying to take advantage of Naruto when he is psychologically weak.