At any time during your game (when you are in the house of a Sim) press and hold B, then press Up, Left, Down, then Right, then you will hear a chime. You can then release B and within seconds, the Cheat Gnome will appear in front of your house near the sidewalk. You can then select him repeatedly for 10,000 (actually 9,999) Simoleons each time!
You can then go to grab mode and place him in the inventory, if desired. No effect, just for fun.
Hold B, press Up, Left, Down, Right.
Skill cheat and 6 hour advance
You don’t hvae to be holding b or anything. Just for the 6 hour advance press right on the d-pad five times and the press left. For the skill cheat on the d-pad press down 3 times and then up 3 times. You can just go over to the cheat gnome and there will be the option to do those things.