If McCown can't reach a deal with the Bills, he is expected to visit other teams in the next few days, a source said.
McCown, 35, was released by the Buccaneers last week. He started 11 games last season, completing 56.3 percent of his passes for 11 touchdowns, 14 interceptions and a 70.5 quarterback rating.
McCown has been with eight teams since entering the NFL in 2002 as a third-round pick of the Arizona Cardinals. His best season came in 2013, when he started five games for the Chicago Bears in place of Jay Cutler, posting 13 touchdowns, one interception and a 109.0 quarterback rating.