You would probably only be able to again around 1 or 2 quality per player at this age for training over a course of a season, I bought a 29 year old but at 5*78 quality and when I sold him 2 seasons later he was 4*81 so he didn't do too bad while he was 29 and 30 while at my club.

Plus he scored about 25 goals from ML for me while I was in L11 and L12 and he was only bought for 1T from transfers so he was one of my best bargain transfers I ever had.