And If You Ain't No Punk...

She gives me money!

According to Access Hollywood and TMZ.com, Lachey reportedly had the papers drawn up by a lawyer before the pair exchanged vows in 2002, when he was the more popular of the celebrity duo. But Simpson allegedly refused to sign the documents.
...
Several publications put the couple's joint worth at around $50 million, and under California law, Lachey would be entitled to half of whatever the couple made after their marriage, unless they reach a settlement.

To paraphrase Kanye West:
If you aint no punk holla We Want Prenupt
WE WANT PRENUPT!, Yeaah
It's something that you need to have
Cause when she he leave yo ass she he gone leave with half