I've started a file recently with Wolfsburg, and I had a budget of 10 million. I then signed about 7 players by offering £0 upfront, plus anything up to 10 million after the player has 50 league appearances. This enabled me to gain 7 players without actually spending a penny of my actual 10 mil budget. Then a few seasons later when they were at 49 league appearances, I dumped them all in the reserves and sold them in the next transfer window for a substantial profit. They were all wonderkids and improved a lot with me, I made about £60 million and my next budget was about £70 million, and now I'm a top team in Europe.