Mariah Carey and Fiance James Packer Lease Mansion for $250,000 a Month

Mariah Carey and fiance James Packer are spending $3 million in rent a year for their fancy new digs.

What's $250,000 a month in rent when you're a billionaire?

Mariah Carey and her fiance, 48-year-old billionaire businessman James Packer, will be living together in an upscale gated community called The Oaks in Calabasas, California, ET can confirm. Emil Hartoonian from The Agency -- a luxury real estate brokerage and lifestyle company -- brokered the deal that has the couple paying around $250,000 a month (or $3 million a year) to lease the mansion.

"The deal was done in just a few days," a source tells ET. "The couple was not looking at homes for a long time. This is just the perfect place for Mariah and her family -- it's safe, it's secure, it's home."

WATCH: Nick Cannon Reacts to Mariah Carey's Engagement With Hilarious Meme

Undoubtedly, the 18,000 square feet estate with sweeping views is impressive. The mansion contains a theater, sauna and gym, and all the stones making up the house are imported from Italy, our source says. Carey and Packer also have the option to purchase the estate, which has never been on the market before.

The family-friendly estate is ideal, given that the 45-year-old singer has two children -- 4-year-old twins Monroe and Moroccan -- with her ex, Nick Cannon. Packer also has three children from his relationship with his ex-wife, model and singer Erica Baxter -- 7-year-old Indigo, 5-year-old Jackson, and 3-year-old Emmanuelle.

Of course, the newly engaged pair is going to have some equally famous neighbors. The Kardashians, Drake, Will Smith, and Britney Spears are just some of the celebs who have homes in Calabasas.

NEWS: Mariah Carey Rents Impressive Malibu Mansion -- From Airbnb!

Clearly, money is no obstacle for the wealthy couple. Packer proposed to Carey last Thursday with a stunning 35-carat diamond and platinum engagement ring, designed by New York-based jewelry designer Wilfredo Rosado. The massive ring beats out pretty much all celeb engagement rings in size, including previously much talked-about bling like Kim Kardashian's Lorraine Schwartz cushion-cut diamond ring from husband Kanye West, and Beyonce's 18-carat Lorraine Schwartz diamond ring from husband Jay Z, valued at over $5 million.

Watch the video below for more on the truly one-of-a-kind ring.