WILL SMITH'S trailer on the set of "Men In Black 3" is nicer than most people's HOMES!

--It's a $2 million, 1,150-square-foot rig with marble floors, a lounge and bar . . . a movie room with a 100-inch screen . . . an all-granite bathroom . . . a large bedroom . . . and offices for Will's assistants and writing staff.

It's 53 feet long, has 22 wheels and weighs about 30 tons. He's renting it for $9,000 a week.
Oh, and Will is also renting a 55-foot trailer with a full gym inside.

There was just one problem with the trailer: The movie is filming in Manhattan right now . . . and the locals hated it. One resident said, quote, "The smell that comes along with it is disgusting. It's like living in a gas station."