Houses are like cars. When you build an expensive house (or car) for someone who is rich, they leave a lower-cost used home (or car) behind, available to be filled by someone who is not so well off.
Except they hang on to the lower cost used home and rent it out at extortionate prices to help pay for the expensive house.
Except they hang on to the lower cost used home and rent it out at extortionate prices to help pay for the expensive house.