well, you're lucky. You seem to have a good transfer market to play with. In my level 2 account I hardly see any players with ratings above 23!!

I have read guides on this forum suggesting that getting older players with higher quality but lower cost is a good option on the low levels. I disagree completely. Young players train faster and their value goes up faster
While you have a valid point, there can be exceptions where selling a young player can greatly benefit you. For example, I sold off a 18 year old defender with 17 rating (he was in my first team) for 700k and with that I bought a 22 rated defender to replace the youngster plus a 24 rated CM. Both were 30 years old but they improved my squad greatly. So I lost an up and coming defender, but I replaced him with a much improved player for instant impact and also getting another strong player to plug a previously big hole in my team. I guess it boils down to what role you want your younger players to have in your team, and choosing between short and long term benefits.

If what you say about values dropping about 15% is true, I think I will not sell off my better young players this season, thanks!