The website claims that Britney has provisionally agreed to do a year-long residency at Sin City's Caesars Palace hotel, where the likes of Elton John and Celine Dion have both performed.
Spears is expected to sign the paperwork at the end of this month, and could start her 80-date at the end of Spring.
Sources claim that personal terms of the contract are still yet to be finalised, with bosses saying she'll be guaranteed a minimum of two or three nights off a week, while she will also stay in the hotel penthouse during the shows.
The 31-year old will need to complete at least two years in order to pocket the full 100million, while a clause also states she must perform a set number of gigs before she gets paid.
It is thought Britney will take home £625,000 per appearance, while tickets are likely to be sold for up to £400.
The Criminal singer is also said to have signed to new management following her split with fiancé, Jason Trawick, with an insider telling TMZ: "This offer has been on the table for some time now and is something Britney has always wanted to do.
"However, she had commitments on the US X Factor and Jason, her manager, was reluctant to over-work her with a residency.
“Now she and Jason have split, her new team have put everything into fast-forward and personal terms have been agreed. It’s simply a matter of dotting the i’s and crossing the t’s now.”
Meanwhile, TMZ adds that Trawick reportedly signed a confidentiality agreement prohibiting him from talking about his relationship with Britney to the press.
He was apparently approached to sign the document by Spears' team when he became her co-conservator, with a source close the ex-couple stating that Trawick would not reveal details of their relationship even without the legal agreement as he still 'respects' the star.
Over the weekend, Spears confirmed they had parted ways in a statement to People magazine, where she said: "Jason and I have decided to call off our engagement. "I'll always adore him and we will remain great friends."
Trawick added: "As this chapter ends for us a new one begins. I love and cherish her and her boys and we will be close forever."