Size is the real question, not temperament
Temperament is never the obstacle with a Maine Coon. This is one of the most easygoing breeds in existence: gentle, sociable, chirping and trilling rather than yowling, and famously tolerant of household life. The obstacle is physical. A mature male can be a metre long from nose to tail tip and heavy enough that ordinary cat furniture bends under him. So the flat question is really a furniture and floor-space question. He needs room to stretch out fully on the floor, turn around in his litter box without contorting, and move through the home along routes that are not obstacle courses. A flat with decent-sized rooms answers all of that; a bedsit where the bed is also the sofa and the desk may not.
Furniture and litter gear at Maine Coon scale
Everything you buy for him needs sizing up, and flimsy versions will simply fail. His scratching post must be tall enough for a full-length stretch and heavy-based enough not to rock when a large cat leans his weight into it — if it wobbles, he will redirect to your sofa, which is a fair trade from his point of view. His litter box should be the largest you can fit, because a box he finds cramped is a box he may stop using tidily. Beds, carriers and any wall shelves must be rated for his adult weight, not his kitten size; kittens of this breed keep growing for several years, and gear bought for the cat he is at six months will be outgrown long before he is finished.
A gentle, sociable cat who needs company
Maine Coons are often described as dog-like, and in a flat that mostly works in your favour: he will greet you at the door, follow you between rooms, sit nearby while you work and join in household routines. The flip side is that he wants that company. A Maine Coon left alone for long days can become flat and withdrawn, so a companion cat, a midday visitor or a work pattern that brings you home at reasonable hours suits him better than total solitude. He is not a high-energy cat, though — moderate daily play, a window view and your presence cover most of his emotional budget, which is why he settles in apartments more gracefully than his size suggests.
Coat care and moderate energy indoors
That magnificent long coat is less work than it looks, because the fur is silky rather than cottony, but it still needs combing a couple of times a week to keep the trousers and ruff tangle-free, and shedding will be a fact of flat life in spring. His exercise needs are moderate: wand-toy sessions, a sturdy climbing tree and games that use his intelligence keep him in condition without needing outdoor roaming. Watch his weight as he matures; a big-framed cat can carry extra kilos unnoticed under all that coat, and feeling for his ribs during grooming is a useful habit.
When a flat is big enough — and when it isn't
The honest test is whether, picturing him at full adult size, your flat still has a corner for an extra-large litter box, a tall post that will not topple, a bed he can sprawl on and floor he can cross freely. If yes, a Maine Coon brings a calm, companionable presence that most flat-dwellers find easy to live with. If every item on that list requires moving your own furniture out, wait for a bigger home. And for the relatives you pick, KinsLe Family Sharing opens his profile to them directly, giving kin further afield their own way in.