Start them at he valuation price.

For example I had a player that I brought for £500k but because I was successful and went up his Value when I sold him had gone down therefore I made a loss and what's worse is he barely got sold on for his value.

I'm sure i'm not the only one who has gone through this at the lower levels of the game, and it makes the game so annoying and frustrating. This particular player had improved ability wise in between me buying him and selling im too which is even more annoying.