If Brady were to play that many years, that would put him at age 45 or 46. The oldest in NFL history to play just QB were 44 years old: Steve DeBerg, Warren Moon and Vinny Testaverde. (It should be noted that George Blanda played until he was 48, but he was more of a kicker at that point).
If Brady were to play six or seven more years and Bill Belichick were to coach for that entire span, that would put the coach at age 70 or 71. According to the Elias Sports Bureau, the oldest to coach an NFL game were George Halas at 72 years, 318 days old and Marv Levy at 72 years, 139 days old.
Brady is currently signed through the 2019 season. If he plays at least one game each season throughout, that would mean 20 seasons with the Patriots.
According to the Elias Sports Bureau, three players have spent at least 20 seasons with one NFL team: Jason Hanson (21 with the Lions), Darrell Green (20 with the Redskins) and Jackie Slater (20 with the Rams).
Tom Brady has 456 career touchdown passes, fourth in NFL history and 83 behind Peyton Manning for most all time. Brady has averaged 2.2 touchdown passes per game the past three seasons, which means that if he played all 16 games in each season at that pace, he would move ahead of Manning during the 2019 season, at the age of 42.
If Brady were to make the maximum amount of money throughout his current contract, which is signed through 2019, his career cash value would max out at $188 million. That's a lot of money. But amazingly, he would be seventh among players who played since 2000 and are signed through at least 2019 (if those players make their max in each of the next three seasons).
Besides restructuring contracts and taking “less” to stay with the Patriots, Brady made $520,000 in his first two seasons in the league combined. Cardale Jones’ contract’s cash value in 2017 is $540,000.