From what you've said it sounds like it could be a complete nightmare as you've potentially got as many twelve totally different rooms, each with their own intricacies. It does sound like a fantastic job though and I'd be fascinated to see how you eventually approach it. My initial thoughts would be that you need a plan.
Firstly you've got the lighting to think about. Does each room have an abundance of natural light? If so, where is it coming from and in what direction is the room facing? Will you be able to rely on natural light for each room or will you have to balance natural and artificial light in order to get a consistent look across each location, should you want it.
And if you are having to introduce artificial light to each room, is there sufficient light already present, in the form of built-in lighting, or will you have to bring your own? If you are bringing your own, what will you need and where will you put it? What sort of look are you going for and does this then restrict you in any way?
And of course you've also got to think about the constraints of each room in terms of focal lengths and the sort of lenses you'll need to use. Are you going to go for a more wide-angle approach to show the whole room off or are you going to look for little details here and there? And are the rooms big enough and spaced out enough to actually let you do this?
Then there's the styling of each room. What's the current state of play? Are you going to be working with what is already there or will you need to bring/add your own? If stuff is already there, has it been styled or is it what the room naturally features? And again, what look are the clients wanting to achieve?
At the very least you're going to need a relatively comprehensive brief from the clients and a good recce or two so you can take some test shots and plan out your actual shoot in detail. It might also be worth considering contacting some local interior stylists to see if they can offer an opinion, or even some assistance. You might be lucky enough to find someone who does this for a living and could therefore benefit from some photography to add to their portfolio.
I know EdTog has some fantastic interior shots on his
website so he might be able to give you some more useful pointers.
