Ferdinand, 35, is available on a free transfer following his release from Manchester United and is set to join Harry Redknapp’s side when he returns from media duties in Brazil.
Former Tottenham centre-back Caulker is another target for the newly-promoted Hoops, but the Cardiff captain is also attracting interest from the likes of Liverpool, Everton and Southampton.
"Rio has agreed to join us and we're hopeful of getting that one over the line when he gets back from the World Cup," Redknapp told Telegraph Sport.
"I can't foresee any problems with it and we'd be delighted if we can get it done soon. He's been a player at the top of the list since he left Manchester United and he would give the whole place a lift with his quality and experience."
Redknapp hopes Caulker, 22, will also opt to head to Loftus Road.
"We've agreed a fee with Cardiff and it's now up to Steven to decide his next move," he said.
"I know him well from Spurs and he's always been a tremendous prospect. Hopefully that's another one we can get done."
Earlier this week, QPR, who were promoted via the play-off final at Wembley, announced the release of Aaron Hughes, Stephane Mbia and Andrew Johnson at the end of their contracts, while midfielder Alejandro Faurlin has signed a contract extension.
Goalkeeper Rob Green and striker Bobby Zamora are also in talks over possible new deals.