Usually, to get a large amount of money in these games, all you need to do is take over another team with the "Add Manager" option and sell a player at a rather unrealistic amount. However, this results in having no players remaining, no transfer budget at your chosen victim club, or even worse, the board keeps intervening. The solution is to take over the team you hate the most with the "Add Manager" option, as usual. However, instead of selling a player to them, have them put in a First Option bid for £100 million. Simply accept the bid and the £100 million is yours with no interference. No matter how deep in debt the club gets, the owners will not stop the transfers, and you can reap the rewards of unlimited money.