First child, we have a small 3 bed semi. It has the classic two double rooms and one box room.
Obv baby will be in with us for first 6 months but I'm thinking it will be easier to designate a room now rather than being sleep deprived and trying to move rooms around.
Currently box room is my office and sewing room. It has built in shelves with a slightly weird configuration to accommodate stair bulk head. Was previously a cabin bed before we remodelled. It's a nice room. I could see a cot or toddler bed fitting in here quite nicely, and could figure out some additional storage. There's a laundry maid for drying things. Disadvantage, smallest room, not loads of floor space, once becomes toddler the built in could worryingly look like good climbing frame...
Spare room has sofa bed for guests, and my boyfriend's office space. It also functions most often as where the laundry dries in bad weather/winter. Nice sized room, but we'd lose our guest room (and where would laundry go! ;) ). Boyfriend really likes having a space to offer friends and family. I feel faint of heart at doing stuff rationalisation ;)
One thought I had was little room when kid is small and big room when gets grown up bed? Not sure about 2nd, will see how I feel and how it pans out conception wise (I'm 37).
Also: how do we baby proof our house, particularly the staircase? It's open to the living room, and has very open banisters... I assume I don't need to worry about this until later and baby is mobile.