If a team goes unattended for 5 weeks, the owner is removed. At that time, the roster is checked for players with high salaries, generally over $6000, but a bit less for younger players, as well as any players who are on national team rosters.
The players are removed from their old team and then placed on the transfer list.
This happens on Monday mornings, local time, and the transfer deadline is set to 3 days plus a random amount from 0 to 24 hours.
The $6000 threshold has been changed from time to time, and the implementation has been tweaked, so that sometimes the older transactions are not recorded completely. If you will check Bohan and Fawcett, their current salaries are over $6000, and their transfer history shows that they were sold a 2nd time 3 days after they were FA on your team. So someone bought them as FA and immediately re-sold them.
Most of the players that are FA are centers (because of the salary threshold). You might be able to find an older player (late 20s or 30s) who you can afford if you happen to be training guards.