Also, this wouldn't be forever, which is what you need to remember, right now you may not be able to move, but if you know this is something you're aiming towards it would probably be more achievable in a couple of years after you had saved up some money.
FWIW, I lived in a one bedroom flat with two children at one time. We had one of those high sleepers that has a desk underneath, took the desk out and put the cot there instead, when we moved to a 2bed house we had a tiny second bedroom, just enough for bunkbeds, and they had toys under their bed in boxes and clothes on a rail on the ceiling.
Now they have their own rooms, but I am pregnant again, and once this one is older DD will be getting the box room, with a high sleeper with built in wardrobe etc, and the younger two will share her room.
The only time DD has ever complained about sharing was when DS was poorly, and he woke her up crying, so he came in with me then til he was better.