It is always best to use young players as trainees, as they are able to train significantly faster than old players.
To achieve the optimal training time, many managers prefer trainees between the ages of 17 and 20, with 17 or 18 the best age to start training.
For new teams 17 year olds with at least Passable main skill should be considered. There is little to be gained from training players that are not at least Passable in their main skill. Instead, training a player who is Passable or Solid in primary skill is not as profitable as training higher skills, but lower skilled players cost considerably less to purchase.
As players age, they decrease in price, so buying slightly older players but more skilled (e.g. 18 or 19 year olds) is a wise alternative solution.
Effect of player age
Clubs at higher series levels may prefer to train older players at a higher skill level in order to remain competitive in both the league and the cup.
Older players are slower to train, and a good rule of thumb is one half extra week for every year older than 17. More precisely, training becomes approx. 4% slower for every year above this (also called trainings speed depreciation).
As a player reaches 27 his abilities may start to decrease. This process doesn't occur constantly, and there is no guarantee it will happen at all. Typically, very small decreases occur for players around 30, considerably larger leaps for players around 35. For some reason, these decreases in abilities always surface on Mondays. Certain skills are harder to maintain as players grow older — scoring ability is the hardest to maintain, whilst goalkeeping is the easiest.
When to cash in
|Further information: Skill trading - to buy players close to "popping" using Total Skill Index|
The better the secondary skills, the more you will pay to purchase the trainee, but the final selling price will also be higher.
In most cases selling trainees at age 21 is the best way to maximise profit. Once a player hits 21 years old, he begins to train at a noticeably slower rate compared to a younger player.
With particularly high skilled players, especially National Team players, training can be taken on further, but in general the financial returns decrease beyond the age of 21.
It is also worth noting it is possible to overtrain a player, and make him unsustainable in the long run due to the extremely high wages. The recent market deflation also makes selling unprofitable after 21.