Old TV show sweepers ...
As is often the case, Hollywood isn't always entirely realistic in terms of portraying lifestyles of their characters inside the worlds they're supposed to exist (don't even get me started on "Friends" and "Seinfeld").
Back in the '70s, though, they WERE much closer to the mark in terms of living arrangements; Archie Bunker's Queens row house was appropriately clean, but shabby -- just what you'd expect from a single-income working-class household. Bob and Emily Hartley lived in a lovely Chicago high-rise, but it was nothing too fancy -- one bedroom plus study (the study, of course, we never saw), bath and a half, small but functional kitchen (I LOVE LOVE LOVE the sunken living room though!). The Jeffersons lived in an appropriately-sized and decorated three-bedroom in a postwar Manhattan high-rise (my best friend once lived in the Jeffersons' actual building).
But as someone who's worked in broadcasting for 25 years, I can say confidently from inside the industry that they were off the mark with Mary Richards. The apartment was certainly lovely (and ever-so-suspiciously *identically* laid out to the Hartleys' Chicago pad, with the U-shaped sunken living room and floor-to-ceiling windows against the back wall -- but of course both shows were shot by same company). Mary's apartment in the early days was a studio, but one of the most beautiful studio apartments I'd ever seen, and tastefully (and expensively) decorated.
No way could a 20-something entry-level television news producer in a market like Minneapolis in 1971 afford such a place, let alone have it so extensively stocked and furnished. How many 25-year-old single girls do you know today who have a fully-stocked kitchen, silver and china service for 8, and the wardrobe she wore?? Frankly, given the hours that news producers work, there would simply have been no time for her to create such a home for herself, let alone the funds to do it with.
If we were keeping with the Hollywood fantasy, then Brian nailed it earlier: she would have had a Hoover Dial-a-Matic. Definitely not an Electrolux; canisters are far too fussy for on-the-go women like Mary. But as long as we're continuing the fantasy, the upright she had certainly would have been the newest and most modern that Hoover would have offered at the time.
Realistically speaking, however, the real-life Mary Richards, just starting out her television career in a new city like Minneapolis, would almost certainly have inherited a 1940s-era Hoover upright from a grandmother or great aunt who just upgraded herself to a top-of-the-line Kirby or Electrolux. Or, being thrifty and resourceful, she would have found a good deal at a flea market or yard sale.
It's not surprising that Emily Hartley would have a high-end Electrolux.
Edith Bunker, however, would certainly be using the same vacuum she got as a wedding gift in 1945 -- whatever Hoover was making back then. Definitely an upright.
At the Jeffersons' residence, I remember Florence using some '70s model Hoover Convertible upright. I remember thinking, though, even as a kid, why -- if they were so "rich" -- did they not at least have a headlight on their sweeper? But that detail aside, a new Hoover Convertible for an apartment like that would have been most appropriate.