Cheat
If you want to earn fast money, just set a player-transfer at 999999999. It will take a wile but it works.
Lots of money
Go to the changing rooms. Click on the chair at the bottom left of the screen. Hire someone for every position.
Click on every person and give them a pay rise. Put it in all nines.
Then go to "Offer contract" and click accept. Their wage will be around -£13m so they'll pay you £13m every week and they'll be super happy.