The most luxurious house: Dr. Mad Dog's house, which I got when I was playing the main task in Woozie casino in LV. Fully equipped, with swimming pool, indoor gym and roof apron. The only drawback is that there is no garage and dressing room.
The most expensive house: LS North, 120000 USD.
There are no duplicate houses in the interior: CJ's hometown, houses for sale in North LV, and hotels for sale in West SF.