It's not 2 years for $18 million. It's $18 million guaranteed. It's $42 million over 3 years, which is a $14 million per year average. Not sure how the contract is structured, but it's probably something like $6 million signing bonus, then $12 million per year salary.
So it's most likely one year at $18 million, and more like $30 million if we keep him for the second year. But the good thing is that we can cut our losses after this year if it doesn't work out.
Btw, PFF gave this trade a "good" grade.