Joey's apartment: This apartment has had many people in it over time. It started out with Chandler and Kip. There are a couple variations of Kips departure, one is that he ran off and got married, the other is that when Mon and him broke up, they couldn't be in the same room and he got phased out. Joey moved in shortly, although he was not Chandler's first choice for a new roomate. He had originally picked a photographer, who had showed up, but Mr.Heckles convinced him that he was Chandler's new roomate. Therefore Joey moved in. When making it big as Dr.Drake Ramoray on Days Of Our Lives, Joey moved in to a bigger apartment. Chandler then got a new Psycho roomate named Eddy. They met in the ethnic foods section at a grocery store. Joey was killed off of DOOL, and had everything reposessed. Meanwhile Eddy was driving Chandler insane. Drying fruit, watching Chandler sleep, accusing Chandler of sleeping with his ex and killing his fish. After several attempts of making Eddy leave, Joey and Chandler put all of Eddy's stuff in the hall, moved Joey back, and pretended that Eddy never moved in. Eddy believed it and we never saw the 'Fruit Drying, psychopath' again. A while later Joey and Chandler won Mon and Rachel's apartment, causing Monica and Rachel to move in. Monica redecorated and made it the best apartment she could. They switched apartments back when Joey and Chandler won Knicks season tickets from M&R. Joey and Chandler were back again. Ross got evicted and temporarely moved in before going to Ugly Naked Guy's apartment. Chandler later moved in with Monica and left Joey all alone. But then Phoebe and Rachel's apartment burnt down and originally had Phoebe moving in with Joey, until they discovered that it was Rachel's hair straightener started the fire. Rachel then moved in. When Ross got upset that he was missing all of the baby stuff Rachel moved in with him. (it was Joey's idea) Joey is still alone now. After some difficulties at Ross's apartmen, Rachel has now moved back in with Joey and is living there currently
Monica And Chandler's Apartment: The apartment used to belong to Monica's grandmother, then Monica decided to illegally sublet it. Phoebe was Monica's first known roomate. After Phoebe got fed up with the cleanliness demanded, she moved out and Monica lived on her own. Shortly thereafter, Rachel came to Central Perk after running out on Barry. Rachel lived with Monica for several years. After losing a game against Joey and Chandler They were forced to move out. Joey and Chandler lived in the apartment briefly. After winning season tickets for the Knicks the apartments were switched back while they were at a Knicks game. About a year later Chandler decided to move in with Monica. Rachel then left the apartment. After a fire in Rachel and Phoebe's apartment, Rachel moved back for about a day. When they found out the cause of the fire, Phoebe then moved into the apartment. Chandler and Monica remained in the apartment the whole time. Chandler and Monica are still living together. Obviously, considering they're married.
Phoebe's apartment: Phoebe moved into her grandmother's apartment after leaving Monica's, one piece of rewired furniture at a time. When her grandmother passed away Phoebe was left alone for a while. Rachel moved in with Phoebe in season 5, and lived there up until the hair straightener fire. Phoebe moved back into the apartment when it was ready, but because of the skylight it was a one bedroom apartment, and she would be the only one living there. Mike almost moved in, but Phoebe and Mike broke up in the process. As you hopefully have noticed, they are now married, so needless to say, they are living together once again.
Ross's Apartment(s): Ross lived in his first apartment with Carol. She then moved out and left Ross living alone. When Ross was with Emily, they left the old apartment, but when he got divorced he had to move in with Joey because Emily's relative wanted the apartment back. Ross then moved into Ugly Naked Guy's apartment, obviously without Ugly Naked Guy. Rachel moved in with Ross in preperation for the baby. When things weren't working out she moved back in with Joey, and Ross once again is alone. He is still living on his own.