I've set up studios in houses, warehouses, apartments, industrial spaces, you name it.
First, what's your budget? Sometimes you can find a place for free and it'll work for months or years before you have to re-locate.
Anyhow, once you settle on budget and start looking, it's probably best to reserve design ideas until you start actually seeing spaces. When you walk in, start making notes! I wear a size 12 shoe, so I walk the rooms heel-to-toe to measure the room dimensions. It helps to write this stuff down. Once you have the dimensions, go home and map the thing out to scale. NOW you can start designing your studio.
Do this with every space you visit, and then you can start assessing your options-price vs. location (security is a major concern when you have rooms full of expensive gear and people coming and going)vs. actual space/need for construction, etc.
Will your new landlord allow you to build walls, etc? That is another concern.
For me, whenever I walk into a place, I consider this stuff anymore. it's a weird obsession: "how would we turn this into a studio?" Sometimes you see a place and it just makes sense, other times not so much.
Houses can be real good, ideally though(if you have the budget) renting some sort of commercial/industrial space or warehouse allows you the freedom to design and build almost whatever you want. Of course, this gets expensive.
Mostly, what you want in you studio is a control room for your gear, and preferably, a seperate cutting room (or 'live' room). An isolation room or two is nice, though not necessary.
If you're building, then focus on your control and cutting rooms first. You can always add more rooms later if you're building. It's nice, though not necessary, to have a window between the control and cutting room.
Acoustics and isolation are important-but remember these are two different things. I've seen people spend lots of money on Sonex thinking it's soundproofing. It's not.
Sonex (and products like it) are used to treat the acoustics inside a room. They do not prevent sound from escaping the room. That's gonna require some serious construction to create an isolated space.
There's some good books about this stuff, I'll have to dig into the library and get you some titles. I could write a book on this stuff (and almost started to here, sorry)based soley on my ecapades in the recording world.
So first, you gotta figure your budget, what sort of gear you're planning on using-for instance, a computer-based system means you can use a smaller space...if you've got an old reel-to-reel and mixing board, you'll need more space just to put the thing. Either way, don't make the control room too small. Guitarists might want to cut in that room (with their amp tops close at hand, and speaker cabs placed elsewhere), five or more people could be in there at onceto argue/help with a mix, somebody might loan you an old console that you just can't say 'no' to (I know this sounds farfetched, but with studio gear, a lot of times people would rather see it get used than sitting around collecting dust). I know of several people who had studios and did not own one piece of gear-but they had a space...hey, my brother-in-law has my studio crammed into his tiny apartment!
