Do believers have to go through a long training period like Roman adopted sons did?

Les explains that in Greek and Roman adoption, a father would train his young son, possibly in his business, so that when he became of age he was tutored and prepared to come alongside the father with full responsibility. That was the right of adoption in those cultures. However, Les teaches that for believers, the moment we are saved we do not have to go through a whole long period of training and preparation. Instead, God immediately positions us equal with Christ the Son, a joint heir. This is all by the grace of God, who predestinated us to that glorious position of being right with Christ in the body, in Christ, and in that elevated position in the heavenlies. Les says we are predestinated unto the adoption of children by Jesus Christ to Himself, immediately placed as the tutored child was with his Father. He notes this may put the average believer to sleep.