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It's her birthday and she can buy if she wants to! Kim Kardashian is turning into a regular real estate tycoon ... she just bought the home next door to hers.

TMZ has learned ... Kim closed on the SoCal home for $7,000,000 and will be expanding her already spacious property in a beautiful neighborhood near Los Angeles. Backgrid

Her current house is undergoing a big renovation, so this marks just the latest real estate change for the reality star ... who celebrates her 45th birthday today.

The new place is reportedly a 4-bed, 5-bath, 4,945-square-foot home with fireplaces, a spa and a killer view, with horse trails nearby.

Contrary to a recent online report ... we hear Ye 's basketball court gifted to him by Kim when they were together was not to

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