My first large sofa was a secondhand three seater that technically fit the room and practically ate it whole. The lesson wasn't about size, it was about clearance. Nobody tells you to measure the doorway, the stairwell turn, and the hallway corner before you fall for a floor sample, and I learned that one the hard way with a sofa that made it to the building lobby and no further.
If you've got nothing to start from, go for a plain three seater in a mid tone fabric, something with legs you can see rather than a skirt that hides the frame, because you want to be able to check what's underneath before you commit. Flip the cushions, press down on the frame near the arm, and if it flexes or creaks like it's thinking about giving up, walk away. A large sofa is the piece that sets the scale for everything else in a living room, so starting with something calm and a little boring is smarter than starting with a statement you'll be stuck looking at for a decade. These work best in rooms built around gathering rather than passing through: a family living room where people actually sprawl, a basement that doubles as a movie spot, a sunroom in a house where three people and a dog all want the same six feet of cushion on a Sunday afternoon. Winter is when a large sofa proves itself, when everyone piles in instead of scattering to separate chairs, and in a rented apartment with an open plan layout, a big sofa can do the job of defining the living space without a single wall needing to move.
Where it goes wrong is in anything narrow or chopped up: a shotgun style apartment, a room with a low radiator under the window, a space where the dining table is already fighting for the same six feet of floor. I put one in a reading nook once, at a friend's place, more out of hope than measurement, and it turned a bright little corner into something closer to a furniture storage unit. Large sofas also clash with a room full of other big, soft shapes, an overstuffed armchair and an oversized ottoman all competing for attention make the room feel like it's wearing three coats at once. One big soft piece per room is plenty, let the rest be smaller and firmer.
The mistake to avoid is buying on the showroom floor plan instead of your own. Showrooms are enormous and forgiving. Your hallway is not.