Fury delivered a brutal sixth-round knockout of Dillian Whyte at a packed Wembley Stadium to retain his WBC heavyweight title in April.
Either side of the all-British fight, Fury repeatedly stated his desire to retire and maintained his career was over after remaining unbeaten in 33 fights.
The 33 year-old has since reiterated he is "very happy" out of the ring after the WBC stated it wanted clarity over the world heavyweight champion's future.
But Fury has backtracked on his initial standpoint, suggesting he would face the winner of Usyk and Joshua's September 21 rematch in a unification bout for the right price.
Asked on talkSPORT whether the reports were true he had offered to train Joshua before his clash with Usyk in Saudi Arabia, Fury responded: "I'd train him to beat Usyk very easy, but he doesn't want my help because I would definitely train him to win and he obviously doesn't wanna win.
"I wouldn't tell you [the game plan] because that's giving the secrets away. But probably you'll see what I'll do.
"Because when this little middleweight batters the bodybuilder again, he's gonna lose again, then they're gonna call for Achilles to come out. They will call and groan for Achilles to come back.
"And I'm gonna say, 'Get f***ed, I'm retired, I don't wanna fight'. And then, when they're begging me to come out of retirement, I will return, but it's gonna be very costly like I said.
"I'll show you how to deal with a middleweight!"
While Fury referenced a significant payday to entice him to fight Usyk, he claimed he would face Joshua on for free at Wembley should he win the bout against the Ukrainian.
"Anthony Joshua's a s***house and I'll knock him out," Fury added. "If he beats Usyk, he's gotta fight me for free in England, for the fans.
"Not for hundreds of millions abroad in a foreign country, here, in the UK. Free-to-air TV, free tickets, sell out Wembley. It'll be watched by 30 million people for free.
"No pay-per-view. No money earned. We do this one for the fans of the UK. Let's see who's the real man of the people.
"I know I am, that's why I'm willing to do it for free in the UK, but he will not wanna do that, he'll wanna travel abroad because he's a businessman and I don't give a f*** about business."