When does NFL free agency start, how does it work and what are the rules?

Kirk Cousins could become a New England Patriot or Atlanta Falcon.
Or Cousins could choose to remain in Minnesota, staying with the Vikings and taking a hometown discount as NFL free agency kicks off.
Outside of the regular season and playoffs, this is the busiest time of the year for the biggest sport in America.
Chris Jones, Josh Allen (Jacksonville), Brian Burns, Mike Evans, Saquon Barkley, Tyron Smith, Danielle Hunter, Antoine Winfield Jr. and Cousins top the list of of athletes who could be on the move in mid-March.
The hour-by-hour build up to free agency has become known as the NFL's 'silly season,' with rumors constantly flying, misinformation intentionally being spread, and national reporters breaking news that was set up during the 'illegal tampering' period that centers around the Combine.
NFL free agency is a frentic blast that annually sees some of the biggest names in the league suddenly changing teams, allegiances and fanbases on a moment's notice.
Here is talkSPORT's closer look at when free agency starts, how it works and all the detailed rules.
The NFL Scouting Combine -- which is the nationally televised set up for the multi-day NFL Draft -- is the unofficial start of free agency.
Every year, college prospects, pro head coaches, general managers, scouts and agents convene in wintry Indianapolis, Indiana to a formal gathering that is mostly unformal.
This year, the pre-draft Combine is scheduled for February 27 to March 4 at Lucas Oil Stadium, which is the football home of the Indianapolis Colts.
While players sprint through a 40-yard dash, pump iron on the bench press and heave balls downfield, the NFL's real movers and shakers privately chat at restaurants and bars in downtown Indy, all in the hope of tentatively finalizing blockbuster contracts that will be announced at the start of free agency.
When an ESPN or NFL Network reporter announces "breaking news" on live TV at the start of free agency, the real news is that the huge contract was agreed to a couple weeks prior during the NFL Combine.
This is the big question that NFL teams face as the official start of free agency approaches.
While the franchise tag is complicated -- just ask -- the reality is that it can be a win-win for teams and players.
A decision must be made before 4 p.m. Eastern Time on March 5 whether a club will "designate franchise or transition players."
Teams can save money by applying the franchise tag for a single year, instead of handing out a monster contract to a player a club might not want to commit to long term.
Players can benefit because they receive a large single-year paycheck with theoretical job security, then they can still hit the open market in the future.
By figuring out whether or not to use the franchise tag before free agency -- each team can apply one franchise tag per year (exclusive or non-exclusive) to a player scheduled to become an unrestricted free agent -- it's easier to go shopping within the confines of the league's salary cap, which is set at $255.4 million per club in 2024.
Prescott received an exclusive franchise tag worth around $33 million from the Cowboys in 2020.
A year later, the franchise QB signed a four-year, $160 million contract with Dallas.
The NFL salary cap rose more than $30 million for the 2024 season, which is an unprecedented rise.
While Taylor Swift might deserve some credit for America's game raking in money last year, it's obvious that money will fly fast and easy at the start of free agency.
The big signings normally happen in the initial 24 to 72 hours, with some of the biggest additions announced as soon as the 2024 league year and free agency signing period starts at 4 p.m. ET on March 13.
Planned trades can also be finalized at that time.
Football's show-me-the-money tour begins two days prior, with a noon ET kickoff on March 11.
The NFL states that "clubs are permitted to contact, and enter into contract negotiations, with the certified agents of players who will become unrestricted free agents upon the expiration of their 2023 player contracts."
Following a two-day negotiating period, it's finally time for the real thing.
At 4 p.m. ET on March 13, NFL free agency will kick off.
Many of the big contracts announced will have been agreed to weeks before at the Combine.
Once free agency settles down, a flashy Draft on prime time TV isn't far away.
This year's amateur selection process is set for April 25-27 in Detroit.
The NFL has become a year-round sport, despite only playing 17 games a year.
For many fans, the free agency circus leading into the draft has become the highlight of the annual calendar.