My 2 cents, set a "free" number of free agent actions. Such as each team gets 5 moves or 10 moves or whatever. Then extra moves cost.
I think it would be s**tty if players on your team get hurt and you have to pay extra to fill out your roster...Espicially if you are out of the running for playoffs,w ouldn't you just not do anything with your team? ie why throw money at a losing team.