What happens the moment someone becomes a believer according to Paul?

Les explains that Paul’s word “adoption” pictures the Roman and Greek custom: a child born to the husband and wife was placed under tutors, educated and trained, and prepared to come in at an equal level with the father, then went through the rites of adoption. The Hebrew counterpart, the Bar Mitzvah at age fourteen, was not on the same level because Greeks and Romans were in the secular world, preparing the child to be a co-worker in the business. But Paul teaches that at the moment we become a believer, we do not go through years of tutoring and training; we are immediately placed as an heir with the Father and the Son. This predestination was not to heaven or hell, but as a believer to that position with Christ from day one, as a joint heir in the process of adoption. Ephesians 1:11 says we have obtained an inheritance and are joint heirs with Christ. Les notes that if you are a joint heir, there are other parties; in the secular economy, if the other half passes off the scene, the heir ends up with it.