ofcourse you can, by upselling them from lower level team
if you have 2nd account with lower level than your main team, you can buy 18 yr/o player from your 2nd account,
the example as below, i got this player free from youth,
look on all his skills which below 20%
if i train this player (only specific skills) until he become overall 139%
and if i have another account which 2 level higher than this account, this player will be seen only 99% and can be sold,
and those below 20% will become 1%.
this is how they do.