Qualifications
Being sturdy with a tough head is the most important quality in a rugby player. You need to be strong, fast, have good hand-eye coordination, and be able to take a punch or a pile-up.
Rugby players spend hours in the gym lifting weights to build up muscle. They eat a high protein diet to keep up their energy. They're very conscious of their health, because without it they're sitting on the sidelines instead of helping their team win games.
You also need to be young. Your twenties and early thirties are your prime playing years. Not too many people can make it to their late thirties, let alone their forties. There's a reason there aren't many old rugby players out there. Those who can stave off serious injury into their later careers are exceptionally lucky, but their bodies can only take so much wear and tear before it's time to pack it in—and ice it up.
Oh yeah, and most importantly, you need to be living in England, France, Australia, or one of the few countries where they actually have a pro rugby league—so, not America.
This is a short-lived career, so it's best to get a college degree behind you, play in college, and have a more stable career you can make a living at into retirement age. We're just giving it to you straight, as is that 280-pound forward rushing at you at forty miles per hour.