Justin Bieber Buys Calabasas Home -- Mayor Totally Stoked

Justin Bieber has haggled his way to Calabasas by purchasing a $9,000 square foot mansion.

TMZ has learned ... after negotiating back and forth with the seller -- who wanted $7.5 mil -- Justin inked the deal for a little more than $6 mil. He'll get the keys by the end of June.

The Mayor of Calabasas, Mary Sue Maurer, couldn't be more thrilled, telling TMZ ... Justin is welcomed to Calabasas and his privacy will be respected just like everyone else's." Thing is ... Justin's privacy problems are not at all like everyone else's.

One of the big attractions for the Biebs -- the property is nestled in a gated community that has not just one but two security gates.

The weird thing -- Calabasas is a suburb outside of L.A. -- 22 miles from the heart of Hollywood. You would think an 18-year-old gazillionaire would like the action, but he seems to get plenty of that anyway.