Assuming he doesn't have any career ending type injuries he shouldn't have to work after football. Worst case should be that he makes his guaranteed money with the Bills and then catches on elsewhere for a few more years at $500k.
He's not "set for life" in the same way the stars are but he should be able to have a comfortable life without working again. Definitely the case if he sticks for all 4 years of this contract.
If he immediately moves to Panama, Costa Rica, the Dominican or somewhere else the US dollar goes a long way he may not have to work. if he buys a profitable business and invests very wisely he may not have to work. However, he should plan on working.
He's in the 40% tax bracket. Add in state income tax (NY has one right?) and he's bringing home roughly half of what he is "paid".
If he actually gets paid the full value of the contract, he'll have brought home about 3.5 million, and will be 31 years old.
They don't get an NFL pension until 55, and that amount is roughly $500/month for each season. I don't know how his injuries effect that (lost 1-2 years) but if he plays 10 years, he'll get about $5k/month. Sounds nice, but that $60k/ year will be in 2043 dollars (pension may adjust for inflation, I don't know).
So if he didn't work after football, he'd have to live 28 years on $3.5 million. That's $125k/year after taxes. This is where perspective becomes important. If you're used to raising a family of 3 or 4 on $125-150k year, then $125k/year as a single guy sounds incredible. If you're used to being a single guy, bringing home $250-$300k a year, and then are told you have to cut your spending in half, while you have as much free time as you want, (since you're not working), then you may have a hard time "living within your means". If you plan on having a family, someone will be working.
It's a great story, walk-on, endured injuries, and now gets a very good contract for his position/role. We should all be proud of him as a Husky. He's done well for himself, all I'm saying is he shouldn't plan on retiring after football.