Gangsters [cheats updated]
When at the Lieutenant Section Type I LOVE HANSON (all caps) to get $50,000.
In the Gang Organizer, go to the city maps. Bring up the info on any business and let the mouse hover around over the box until a little 'Return to base' tip appears. Click there and tada, the business is yours. If you want, you can sell it on the spot and the cash will go directly into your assets. Or you can wait until next week when you can send someone to run the business.
$3000 For Gangs:
At the Lieutenant part of the gang organizer screen press D + A + R + T to give $3000 to each gang.
Extort some properties (it will not matter if they want to pay you the money). After that week, look on the map and double click on the property that was extorted. A picture of the owner will appear with details about the shop. Move the cursor next to the picture in the "blank space" and the cursor will change. Click when this happens and the property will become yours. Do not forget to send a man to run the place the following week.
Go to the Lieutenant's page of the Gang Organizer, open the Cars menu, and go to the "Black Market". Instead of clicking on the car you want and waiting for the money clip to appear, quickly drag the car of your choice from the "Black Market" page to the picture of it on the Lieutenant's side. If this was done fast enough, the item will be yours, with no money being subtracted. This can also be done with guns, but does not work with recruited hoods. Note: Try this first without having enough money for the object, as it takes some practice. After each time this trick is used (whether successful or not), exit the "Black Market" and return.
At any menu, type GIVEMESCORPIO (all caps) for Scorpio League or GIVEMETAURUS for Taurus League.
Alter Game Speed:
At any menu, type WARPSPEEDMRSULU (all caps) for Hyper Speed or WRECKEDONSPEED for Mega Speed.
At any menu, type FLYMETOTHEMOON (all caps) for Medium Gravity, JACKIMFLYING for High Gravity or BRINGMEBACKTOEARTH to restore Normal Gravity.