After a made basket, Team A is set to inbound the ball. Team A's strategy to break the press is to have another player standing in the out of bounds area. Sometimes this player receives a pass and sometimes he doesn't.

I know it is legal to pass to him, but what happens if the ball is inbounded as normal? Does the additional player have to be back on the court by the time the ball is in possession? I have been told that it is a throw in violation if he has not established position on the court by the time his team establishes possession? Any thoughts would be appreciated.

I'd challenge whoever told you that to show you the rule. There is no such rule. Give him a reasonable amount of time to get back onto the court.

Probably by a coach or parent - or both.

Throw-in violation
 

No violation but both out of bound players have to return to the court immediatly.