First find a rich family that have enough money to buy the big mansion house you want then sell all there stuff in there house for extra money. Then save the game and go back to the neighbourhood you were in then move that family out of their house and into mansion house that you want. when you have done this save the game again and go back to the neighbourhood now make your family that you want to live in the big house and move them into the same house the others are in it will combine the 2 families together. now buy a computor and tell 1 adult sim to click find own placenow simply click on all the sim charecters that you dont want to keep (from the old house) and they will m,ove out leeving your family in the big house and with all the spair money left wich is usually between 50 and 100 thousand pounds now decorate your new mansion home and enjoy your new rich life

this cheat is a great way to get the biggest homes in the neighbourhood trust me it does work.