Jason Statham & Rosie Huntington-Whiteley -- Takin' The Next Big Step ... A Ballin' Bev Hills Hideaway

Jason Statham and his supermodel GF Rosie Huntington-Whiteley are finally taking the big plunge ... by going halfsies on a ballin' $13 mil Bev Hills estate.

There's only one sure way to know Hollywood love is real ... shackin' up. Our real estate sources say the action star and his leading lady went 50/50 on a sprawling 5-bed, 8-bath, 7119 sq. ft. mansion that even has a waterfall pool.

The timing is perfect -- they just celebrated 5 years of love. And the plot thickens, because Rosie's been sporting what looks like an engagement ring since December.