Buy something really expensive (for example the flat screen tv as its £8,000)

Put it in your house and then put it in your storage. Then click on your storage and click on the button which lets you put it back in your house, before you place the object, go back to the storage and you will see that the tv is still there- click on it and sell it, then get out of storage and you will find that you can still place the tv. Do this again and again, and you will find that you still get the tv, yet you are able to make lots of money (about £4,000 each time i think) just keep doing it and eventually you will have LOADS of money. When your finished, place it or sell it otherwise it will always be in your storage. My sims lifetime wish was £100,000 net worth and in a matter of minutes I achieved this!