@hedgekat1 - It is the 50 x 50 lot on willow creek. You have to buy a lot then you can either go to manage worlds and edit/build on the Oakenstead or have your sim travel to the lot and you can bulldoze it with out exiting to manage worlds. Then you can move household and the lot costs 10000.
Edit : On a side note I like the fact that if you keep the foundation as low as I did on his starter house I didn't need to place stairs so that did not take up much needed space!
Edit Again : Forgot to mention that after finishing Byron's mansion he got heavily inebriated in celebration, saw Nina Caliente and had a one night stand but forgot the love glove and a few days later she had triplets 2 boys and a girl. Frederico Caliente, Poppy Caliente (girl) and Trever Caliente. Even though he had broken up with Nina he moved the four of them into the mansion and has had very little sleep.