Ferdinand, who turns 36 in November, was allowed to leave Manchester United at the end of last season after 12 successful years at Old Trafford.
The defender was a free agent while he worked as a television pundit at the World Cup in Brazil and although several offers came from England and abroad, he was preparing to hang up his boots before Rangers came in.
"If I had not come back to a team in London, I probably would have retired," Ferdinand said.
"I would have done TV, maybe coaching. I enjoyed the TV work in the summer so I would have done more of that."
He continued: "My representatives spoke to a few teams out in America, the Middle East and Europe as well but the main thing was getting back to London and when Harry gave me the call, all bets were off."
Ferdinand is reported to have taken a significant wage cut to join Redknapp's side and the 35-year-old insists he has a special affection for QPR, having played at the club as a boy.
"I could have earned a lot more money elsewhere but the money has never been an issue for me," Ferdinand said.
"People sometimes forget that when you are a kid, you play football because you love playing football.
"This was not about money, it was about playing in a competitive league, in London, for a team I have an affinity with from years ago.
"This was the first club I ever went to as a kid."
Ferdinand left Rangers as a teenager for West Ham after being spotted playing for the district team by Frank Lampard senior, who was on the Hammers' coaching staff at the time.
Redknapp took over as manager at Upton Park not long after and he handed Ferdinand his first-team debut in May 1996, bringing the centre half on as a substitute in a 1-1 draw with Sheffield Wednesday on the final day of the season.
"Any player will tell you, if a manager gives you your first chance in football, they will always hold a place in your heart," Ferdinand said.
"Harry was always supporting me, singing my praises, telling me off when I needed to be told off."
Ferdinand continued: "We've stayed in contact ever since. We would sometimes go six months without speaking but when I've seen him it's like it was back in the day.
"There has always been a connection. He has not changed much, he has not even got any grey hairs."
The former United man is likely to be paired in central defence alongside Steven Caulker, who has been brought in from Cardiff and is 13 years Ferdinand's junior.
Despite being let go by United, records showed Ferdinand was the fourth highest in the Red Devils squad last season when it came to being fit and available for match selection.
"Some people question my fitness but over the last two years I have been one of the most ever-present in terms of training and games," Ferdinand said.
"I thought I could play every Premier League game last season when I was at Manchester United but it was not to be.
"I am here now and hopefully the manager will call on me every week and I can produce."
He continued: "Harry told me to play as many games as I can.
"The amount of experience I have got, if I can be of help to the young player here by the way I train, the way I conduct myself, then that is great."
Ferdinand won six Premier League titles, an FA Cup and a Champions League trophy during his stay at Old Trafford and has been capped 81 times for England.
A potential relegation battle at Loftus Road will pose a different challenge to what he has been used to previously but Ferdinand insists survival with QPR would be another achievement to add to his list.
"All I play for is winning trophies - I am not silly enough to think we are going to win the title but hopefully we can have a good cup run," Ferdinand said.
"I will not be feeling that buzz here but staying up will be an unbelievable achievement.
"If I had gone to some of the clubs who were interested in me, there would not have been anything to play for.
"Staying in the Premier League would be an amazing achievement."
Ferdinand remains open to the possibility of a coaching career after he retires.
He is currently completing his qualification badges but will focus entirely on playing while at QPR this season.
"He brings a bit of class to the place," Redknapp said. "He's a class act on and off the field.
"On the training ground he'll be a great role model - the way he conducts himself, the way he trains, the way he looks after himself.
"He'll be great for me and he'll be great for the club."
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