Walt was already just like Gus, he just hadn't realized it yet.
Also, Jesse was already a decent guy with a conscience. He was a criminal but never a violent criminal, and he was only a criminal because he was a lazy slouch without motivation to do anything but follow the path of least resistance. He only killed Gale because he needed to pay back Walt for saving his life.
And yeah, in his situation I would have taken their money. But I would have really, really hated doing it. And remember, in season one Walt still wanted to manufacture drugs without violence. In season 1, I think Walt was still genuinely sympathetic.