2002 Altima with a lot of valve train noise

Hi guys, I've got a 2002 Altima 3.5L that has a lot of valve train noise when it is cold. Most of it goes away after running for a while but its bad. I'm trying to sell the car but I know this will be a problem. Is there any easy way to quiet this noise with out taking it to a dealer or repair shop. Has anyone else had this problem? Is this a common thing with the 3.5 because my 00 max with the 3.0 is as quiet as a church mouse.