Britney Spears takes the stage to present an award at the 2006 American Music Awards in Los Angeles in this Nov. 21, 2006, file photo. Spears completed a month in rehab, which cost ,600 per night at Promises Center in Malibu, but she still has plenty of money in cash, property and endorsements, according to leaked documents.

Britney Spears may well have found her stint in rehab taxing, but her biggest challenge lies ahead: Settling her divorce from Kevin Federline and fighting the complex custody battle over their sons.

There’s good news for the troubled pop tart. With an estimated net worth of $100 million, Britney can easily afford the $48,000 bill for her month-long stay at one of the nation’s poshest rehab centers.

Though her fortune will be slightly dented by an expected seven-figure payoff to Federline, she’ll still have enough to cover almost a lifetime of treatment at the $1,600-a-night Promises Center in Malibu, Calif.

But the star – who not too long ago was on top of the music world – would be wise not to hang up her microphone for too long.

“The best thing Britney can do right now is take some time away for herself and make a great record,” says Joe Levy, executive editor of Rolling Stone magazine.

“The old saw is that she’s just one hit away from a comeback. Side by side is the saying that there’s no such thing as bad publicity.”

The drop in sales of her previous albums doesn’t necessarily mean she has fallen from favor because record sales have declined across the board, says Levy. “I think it is still possible for her to run her business.”

And what a business it is. Divided into a string of separate companies, such as Britney Touring, One More Time Music, Fairy Zone Productions and Britney Online, it’s more of a corporation.

“She’s a very wealthy woman and protected by an ironclad prenuptial agreement,” says financial expert Lea Goldman, associate editor of Forbes magazine, which recently ranked Spears as the 12th-richest woman in entertainment.

Fortunately for Spears, her income will continue to grow, whether she goes back to work or sits on her butt.

Under the terms of her 2005 perfume contract with Elizabeth Arden, she gets a guaranteed sum of $2.54 million this year, even if, as Goldman predicts, sales fail to meet expectations.

“Midnight Fantasy, the latest perfume in the range, looks like it’s going to be a bomb,” says Goldman. “It came out at Christmas around the time she started spiraling out of control.

“The campaign isn’t working because the gorgeous advertisements of a blond, thin Britney are completely out of sync with the tired, out-of-shape mess we are seeing in the tabloids.”

The headache won’t be the star’s, however. Even if it were, the hundreds of thousands of dollars she’ll collect from other sources make the perfect tonic.

Royalties, merchandising, past endorsement deals and revenue from properties produce hefty annual handouts and, wisely invested, will earn large amounts of interest.

Britney’s finances are supervised by an elite group of bankers and accountants who have skillfully managed her funds for a number of years.

Sources say she follows their advice to the letter. What a shame they don’t have as much influence over their wayward client’s private life.