If you need just a little money, enable the move_objects on code. Have a Sim repeatedly get a snack, but cancel it before they start eating. They will put it on the floor. Then, enter buy mode and click on it. A message stating "Press Delete or click here to sell Chips for $15" will appear. The snack only cost $5, so you get a $10 profit.
Keep evicting your Sim until the net worth is as much as desired.
Enable the move_objects on code, then go to build and floor tiles. Got to the end of the road and hold CTRLand click. Drag down the road to sell it for easy money.
Buy a house that has walnut doors in it. You can sell them for 160 Simoleons, even though they are originally priced at 100 Simoleons.
Enable the rosebud code to get some money, then move your Sims into a lot that has two roads, visible from the lot. Enable the move_objects on code. Go to build mode and select the most expensive carpet. Put the carpet down only out of bounds. Save the game and go back to the neighborhood. Create a family. Move them into the same lot that you just modified. The extra carpet will not cost your Sim any extra money. When you get to the lot, enable the move_objects on code and sell the carpet. You will get about 20,000 Simoleons every time you do this. Repeat this until you have a desirable amount of money. Note: This lot will not have a road, but your Sim will not know.