Found this that says, Miami, Skins and Broncs are the three and confirms what SS said about guaranteed money.
Has Manning already narrowed his choices? - CBSSports.com
One team official that contacted Manning's agent, Tom Condon, says he got the definite impression that Manning indeed has already decided where he wants to go, or, at least, the handful of teams truly in the mix. The official, who did not want to be identified, believes that Miami, Washington and Denver are the front-runners. One report states Manning has already informed the Redskins he doesn't want to play for them.
But the official conceded the front-runner will be the team that, in the end, offers the
most guaranteed money.
The official believes that contrary to some reports, Manning is indeed open to playing in the NFC, even in the NFC East where his brother Eli, is obviously king of the division.