Britney Spears's earning power sinking fast.

Aspiring rapper, Kevin Federline has walked out on his pop star wife, Britney Spears just days before she is due reports Australia's NW MAGAZINE.

Sources say Kevin Federline is so wrapped up in his growing star, that all he thinks about is Kevin.

Now, The National Enquirer is reporting that Britney Spears's earning power is sinking fast.

Five years ago, Britney was ranked No. 1 on Forbes' Celebrity power list and earned $39.2 million — but last year the 24-year-old pop star's income was reportedly an estimated $4 million.

And it doesn't look like aspiring rapper Kevin will be raking in the dough with his new CD. "All of Britney's hype for Kevin's single 'Lose Control' couldn't help his pitiful and embarrassing performance, "a showbiz source told The ENQUIRER.

"After 30 seconds on stage, people were actually giggling at him."

Brit's career is on hold as she takes care of son Sean Preston, who turns 1 on Sept. 14, and awaits the birth of her second child..

And although Britney's far from broke , insiders said she'll never again be the hot commodity who earned huge sums of money in the past.