All players may be placed on waivers at any given time. The penalty or "cap hit" depends on the amount of salary for the player dropped.
If a players salary is: $300k to $750k, that player may be dropped without penalty.
If the players salary is: $751k to 1.5m then the cap hit is 50% of salary.
If players salary is: 1.51m to 3.5m the cap hit is 40%
If the players salary is: 3.6m to 7m the cap hit is 30%
If the players salary is 7.1m to 15m the cap hit is 20%
If the players salary is 15.1m and above the cap hit it 10%
An owner is responsible to pay the cap hit for the remainder of the year regardless if the player is claimed.
The waiver order to claim a player that has been dropped is the opposite of the MiLB draft order. Once a team has made a successful claim they will move to last and all other teams will move up.