Unitas, a 10-time Pro Bowl quarterback who retired from football in 1973, will serve in an as-yet untitled role, Clancy said.
"He's one of the team," said Clancy, who as a youth watched Unitas play at Memorial Stadium and attended the same church as the player in northeast Baltimore.
Clancy's investment partnership includes Hollywood producer and businessman James Robinson and local lumber company executive Lou Grasmick.
The group has also approached another Hall of Fame ex-Colt, tight end John Mackey, about joining. Unitas was unavailable for comment, but his son and agent, John Unitas Jr., said he had introduced himself to all three ownership groups vying for a Baltimore franchise.
The deal with Clancy's group is the biggest yet for Unitas Management Inc., a company headed by the ex-player's son that manages personal appearances, endorsements and other business arrangements.
The agreement with the Clancy group involves personal appearances on behalf of the group and "whatever we can do," Unitas said. "We feel that the Clancy group is the best group for ownership of the franchise. My father has always been supportive of Baltimore."
He and Clancy declined to provide financial details of the agreement.
"That's our business, not yours. But you don't get a guy like this for free," Clancy said. If the group is awarded a franchise, the ex-quarterback "has got a job on the team for as long as he wants," Clancy said.
Unitas, 59, raised some eyebrows in September when he attended a rally for a competing football bid in Charlotte, N.C. He said at the time that he was merely doing a favor for Jerry Richardson, another ex-Colt who is heading that group, and that he still supported Baltimore's bid.
Baltimore is competing against four other cities for two teams the NFL says it wants to add to the league. The expansion is on hold, but the teams could be awarded next year.