Is this decision of Pettitte been influenced by his close friend Roger Clemens or money that matters?
Clemens and Pettitte have been teammates since 1999, playing five years together in New York and the last three in Houston. Also, Pettitte didn’t want to stand the idea of competing against Jeter, Jorge Posada and the other Yankees he grew up with.

Pettitte is Back
He left the Yankees feeling a bit upset because their offer three years ago was on par with Houston’s, a team in a small market with lower taxes. But Pettitte missed New York and probably felt even more welcome when Yankees general manager Brian Cashman passed on a chance to bring back Ted Lilly for $40 million over four years. But now, the Yankees will pay Pettitte $16 million in 2007 and the Astros had offered a $12 million for one year. The Astros Astros had apparently decided not to go higher than that for the left-hander.
Whatever is the reason behind his decision, but one thing is decided that he will be a Yankee this season.