A trick to get money quickly:
Simply create a 2nd club as a shell company. The 2nd club then gives the 1st club very favorable loans, while the shell company borrows the money from the bank. Once the shell company goes bankrupt, it won't be able to make any claims. Obviously, the shell club will lose badly in any direct match.

Tested with versions 1.00 and 1.90.

Trick:
1. Buy stocks with all your capital so your account goes deep into the red.
2. Then get the best stadium upgrades available.
3. For tactics, let the non-existent 4th block play the entire season to finish last in the table.
4. In the next season you'll only have a fraction of the original debts.
5. Go back to step 3 and repeat.
Now you can pay off remaining debts with stocks and credit, and you're the proud owner of a fully upgraded stadium.

If you play on the highest difficulty level, follow this tip:
In the contract options box, set the salary to 1 DM. Set the contract duration to 1-4 years and accept everything. This gives you a complete squad of 29 stars for only 29 DM per month.

When you extend contracts from two to four years at the start of the game, you won't have to pay a penny in salary. Once the contract duration drops to two years, you can extend them again. This cheat only works on the highest difficulty level.