For my house, anything that big would mean something would have to go out. I could give up on my living room entirely and let the couch go... but then I'd still be faced with the issue that I prefer to move the machine than the quilt.
Or maybe we are talking two different things, I'm thinking of something like the Craig's List set-up described as "TinLizzie QueenQuilter 18" Long Arm w/stitch regulator. It is the sit down model and comes with the table for easy fabric movement." That's the thing about doing your research, it's a great set-up for some people, each machine and style and frame has someone that it is perfect for.
I know frames can be set up at smaller sizes as well, but mostly I do queen+ sized tops so would want that full 12' frame. If I had the ability to quilt them down, I do more in the 3-yard square king size top that I never make because I don't want to handle. One of my friends was quite clever, she had a 2-story living room and built out a balcony from the open upstairs hallway to accommodate her long arm! But most have given up a garage or family room.
When my son was little, I figured when he moved out I'd change the family room into my long arm room. But then I got a husband who needs his computer desk every bit as much as I need mine, and truthfully, most days I'd rather have the hubby than the long arm. Most days... My husband is a wonderful man and I am so lucky we met. All in all, I'd rather have a huge dog kennel and a few critters than a long arm.