Physical Danger
Stuff three roasting chickens full of pudding, lock them in a refrigerator, and throw the refrigerator down a hill for three hours every Sunday for four months. The chickens will give a rough approximation of what football does to your body. And as a bonus, carrying the fridge back up the hill is a great way to get in shape for next season.
Death. Taxes. Injuries. Every football player in the world has to deal with all three (hopefully not on the same day). Approximately two-thirds of all NFL players will experience a concussion at least once in their playing careers. As many as 500 players each year will miss at least one game due to injury, and many will have their seasons ended by injuries.
No part of the player's body is safe—fingers, toes, ribs, neck, nose, back, ankle…and that's just Ben Roethlisberger in the third quarter of any game against the Ravens. Because of the high risk of injury in the normal course of a game, the NFL has strict rules against any organized effort by a team to deliberately injure opponents. Ask former New Orleans defensive coordinator Gregg Williams, next time he calls your house to offer you an exciting new opportunity to refinance your mortgage.
The NFL does offer better-than-average health benefits, including dental coverage (which must have been instituted after Jack Lambert retired) and life insurance. Players with at least three years of experience are offered five years of continuing health benefits after retirement. However, since the average length of an NFL career is between three and four years, that leaves many former players with no insurance and an injury history that would make Indiana Jones cringe.
All of that only applies to the NFL, however. Players in smaller leagues who don't get paid enough to quit their day jobs must rely on their health coverage from those day jobs.