To be invincible first you need to do the thing with the controllers and then after that type in XYABXY

First, to enable the cheat codes you need to plug a second controller into port two on your Xbox and then take it back out. Next, on your first controller enter X, X, Y, Y, B, B, A, A. Once that’s all done you can enter the following codes to cheat your way through the game.

Then: On the first controller push down on the left thumbstick twice (as in click it in, not push it in the down direction), right stick twice, left stick twice and right stick twice. You’ll hear a guitar strum confirming that you've entered the code correctly. Enter this code in multiple times for even more Moolah.