Sources familiar with the situation tell TMZ … The "Million Dollar Listing Los Angeles" star is under contract to purchase the singer-songwriter's 5-bedroom, 4-bathroom abode ...  located in the wealthy Trousdale Estates neighborhood.

The real estate investor is close to nabbing this hot property under the radar, as we're told the deal is an off-market transaction. Though, it’s currently unclear what Josh offered to pay Charlie for the residence.

Charlie bought the home from famed American photographer Matthew Rolston in 2017 for $9 million. The home was previously listed for $17 million ... but came down to $14 million when it was last on the market in May 2024.

So, we have a feeling Josh scored himself a deal here.

The manse is certainly worth the hefty price tag, too. The mid-century pad -- originally designed in 1965 by legendary L.A. architect, Rex Lotery -- has had serious work put into it over the years.

Yet, it's legacy as the social hub for Beverly Hills' elite makes the property even more alluring. The home once hosted Ronald Reagan’s "kitchen cabinet" -- AKA the late prez's closest confidants. The home was also once owned by "Tonight Show" producer Freddy de Cordova and his wife, Janet de Cordova.

This isn’t Josh’s first big real estate move. In March 2022, he scooped up a 7,100-sq-ft. Beverly Hills mansion for $9.2 million. Records show he still owns the property.

In June 2023, he made headlines again when he expanded his investments to include a home on Miami’s exclusive North Bay Road.

We're told Josh and his dad, Michael Flagg, who was president of the highly successful family owned women's fashion label, Edith Flagg (named after Josh Flagg’s businesswoman and philanthropist grandmother) are exploring several properties in New York, too ... so his real estate portfolio could very easily expand again soon.