One of the plot lines deals with Miles getting a divorce and temporarily having to live like a normal non-rich person, driving a hatchback (which he calls a hunchback) and living in an appartment. Before (and soon after) Miles is quite affluent, and Fraiser is not far behind.
He's not living in a stereotypical apartment -- it has a large living space (in which he's able to host fairly large parties for the upper crust), a well-appointed kitchen, a separate floor for bedrooms, and a third floor that's never seen on the show.
