50,000,000 cash:
Go to info mode underneath the question mark, and click on one of the towns, then click on rename town and type 'Scrooge' and then click OK. Do this exactly as above and you get 50,000,000 cash to play with. You can do this as many times as you like. Might be worth cutting and pasting it if you want to repeat it.

Hex-Cheat:
Save a GAME after starting with DM 500.000 DM. Now open the savegame with an Hex-Editor and change the Offsets 20a10700 in FF FF FF FF, now you have 4 Milliard Money.