I don't think buying players with re-sale in mind is the way the go, we're not Dortmund. You're not going to see Liverpool shipping off Salah, Mane, Henderson or VVD.
If you do things right, you don't need to sell to buy anyway. If we're serious about giving the academy kids a chance then that's what needs to be in mind when you buy players. The likes of Partey and Sabitzer will be in their 30s in 4 years, Ceballos would be 28 if we signed him too. Azeez and Patino would be 22 and 21 respectively (or if they turn out to not be good enough sign others of that age who are). Age/experience wise that's a midfield with a very good balance.