Is that entire salary guaranteed? No matter what, that is a good amount of cash so good for him! Really life changing.
If for some reason the NFL does not work out for him, his intelligence and attitude will make him a success in life. (He already is)
As you can see above...
-- first-round picks have most of their contracts guaranteed
-- second-round picks have some of their contracts guaranteed
Again, it is not as formulaic as the NBA, but NFL rookies basically have the same "cliff" between the second-round and the first-round as guys do between pick #30 and pick #31 in the NBA in terms of guaranteed money and years on their first contract.
Then again, it is easier to make an NFL roster as a 3-5 round pick versus the difficulty of playing your way onto an NBA roster as a second-round guy.
Looks like David received a $495,000 signing bonus. So he does pocket that. The remaining $3.1 million on his contract the next few years is not guaranteed, though.