What I notice, living in one of three houses built in the same year by the same people is that what you are talking about fades a bit with time. Originally, they WERE generic and identical. Now, the house to the south has a barely usable attic and a deck. My house has a second bathrrom and an extra bedroom off the back, and the house to the north is substantially bigger than either of the others. Of course, this depends on above average wages to occur, and requires room to make the additions.
On the other hand, the subdivisions around us? Not all identical, because they've gotten smarter. Now it's the same 5 houses repeated to make 80. VERY generic.
So I guess what I'm trying to suggest is that your "not rich but decently well off" housing should vary more with age, your rich people all need custom-built houses for the most part, and your poor people need generic shacks.
Easily represented by having several minor "variants" (porches, additions, gardens, shrubbery, different window trim, various curtain styles, etc.), and randomly applying those to some, but not all, of the houses during initial world design. In any given group of houses, most would have at least one distinguishing variation, if not several, and the rare few that had none of them would stand out as equally "unique" because of the lack. Better grade housing would require a bit more liberty and expense shown in the variations (and generally have room for more), where the poorer shacks would mainly differ by such trivial features as flowerbeds, window dressing, and other "cheap" features. The developers could then hand-place a few specific "exceptions", like a basic shack that's gotten a major addition.
A significant amount of basic housing (with varied "generic" furnishings) could be placed quite rapidly throughout the cities in the game after that, all of which would be fully enterable and explorable (not that there would be all that much to find in most), without looking like it rolled off an assembly line. Furniture, dinnerware, storage, and other indoor features could also be done using 4 or 5 "templates" for each style of house, with three or four minor random variations between those (one has a redware jar on a shelf, another has two green glass pots on the shelf, a third doesn't have a shelf, etc.). The combinations could be pretty close to infinite, and the occasional hand-made change would break up the sameness, although the vast majority would still fit a general "pattern".