As it stands now, the Denver Broncos are really only paying Peyton Manning $18 million in 2012 on his new contract. The other $78 million depends on later physicals. Should Manning pass his March 2013 physical the $40 million dollars over the next two years becomes guaranteed, according to Andrew Brandt:
Peyton passing his March 2013 physical activates 40M guarantee, paid as 20M salary in 2013 and 2014.Can be reduced if injury to neck.— Andrew Brandt (@adbrandt) March 20, 2012
If he doesn't pass his physical, the money due to him "can be reduced," according to Branch, but there are no clues as to what that comes out to right now. But if Manning's neck holds up, the quarterback will receive $20 million in 2013 and in 2014.
This is a great contract for both sides since the risks are minimal.