Go to menu where you choose a level, then press Enter and

fill in one of the cheats below and press Enter again. Then in the game press

C.

worker928     in the main menu you can buy a worker
weapens563    your gangster has all weapens
loans458      infinitive loans on he bank
estates216    you can buy all land
houses462     you can buy all houses
build830      the hous you bought will apear     immediately
gadgets215    have all gadgets
upgrade934    you can upgrade immediately
maps029       have all maps
tenants872    have infinitive tenants
pickup036     you can pickup enemy houses   
     

Thanks to Revolution reader Fabian!