CTRL+SHIFT+C
The quite familiar key combo for opening the cheat window (opens at top-left)
rosebud
Adds §1000 to household funds.
rosebud;!;!
Adds §3000 to household funds. Every additional repetition of ;! (semicolon, exclamation point) adds an extra §1000.
move_objects (on / off)
Allows you to move objects outside the buildable grid boundary, objects in use, and normally ungrabbable objects like sims. Take care not to delete the mailbox or the kerbside bin, as you won't be able to get these back. If you delete a sim in your household, right-click their portrait to get them back.
If you want to delete bills without turning on move_objects, have your sim get the mail, then cancel the action from the queue. As she moves to set the bills down on the nearest free ground tile, pause the game, then enter Buy or Build Mode and move another object onto the tile where she's going to set the bills. When you return to the game, she will set the bills down on that tile, the game will detect an illegal object overlap, and the bills will vanish.
If you're trying not to cheat, but you need a sim family to have a much more expensive house than they could otherwise afford, try this...
1. Move the household onto an empty lot, then save and return to the neighbourhood.
2. Go to a different neighbourhood and load the corresponding lot (if your sim family in Neighbourhood 1 lives on 9 Sim Lane, then load 9 Sim Lane here).
3. Build and furnish the house you want the sims in the other neighbourhood to live in, then save and quit the game.
4. Open The Sims/UserData#/Houses (replacing # with the number of the neighbourhood you built the house in just now) and find House##.iff. So, if you built the house on 9 Sim Lane in Neighbourhood 3, you would go to UserData3/Houses and copy "House09.iff". Copy this file and paste it into the UserData#/Houses folder of the neighbourhood where your sim family lives.
5. Reload the game and play in the house of your dreams!
Why does the above exploit work? The house, the occupants, and the household funds are all saved in different files. You can overwrite any one of these without fouling up the other two.
Time at your home lot will stop when you leave it to go to a different lot. If, for example, your sim's mood is lagging after work, you can go Downtown or on Vacation, raise their mood, then return home to the precise instant they left, fully refreshing them for their next day at work. You can leave for another lot at any time, up to the arrival of the carpool.