Just one warning: remember that the salary is affected mostly by the main skills in a player's role, while the training cap is affected by all skills.
So, that means that a very balanced player will hit his cap much sooner than expected. Samurai_Tungi gave you the consensus cap for a 6th man potential player, which is 15k-18k, but the cap may be hit even at 12k if you rotate his training over all skills, for example to turn him into a SF.