Free Players in Career Mode
In Career Mode, select Search Player and look for a player (for example, Neymar). Send a transfer offer with a high value, such as $99 million. Once the player accepts, a contract offer is made. Leave the wage the same as specified, but change the role to "Future 1st team player." Any sufficiently skilled players will decline that offer. Perform a new search for the same player. Now, offer them $0 and submit your new offer. Now, return to the declined contract and change the specified role to "Crucial 1st team player," which the desired player should then accept. You must pay only for their wage.