Alright. So this is going to be a freestanding structure?
I guess a few principles in order. First, stopping sound requires mass. Airgaps also help. That is why you generally do a "room within a room" format if you can afford it and use double layers of soundboard and rockwool. The inside room is often also floating on rubber pads to further isolate it. You want to seperate the various rooms as much as possible with these double ways to prevent spillage (sound going into a microphone it is not intended for) while still having visibility to all rooms from the control room if possible. The control room windows are general double, the two panes should be different thickness and they should be on an angle.
If possible, rooms should not be square and, if possible, walls should be not parallel with each other (helps prevent standing waves)
That should handle soundproofing, inside out and outside in and from one room to the other. The next consideration is sound treatment. You probably want a variety of sounds in various recording rooms, from a natural reverby (live) room to a more dead vocal room. You can do things with movable panels to have flexible rooms as well (foam one side, reflective surface the other). In general, high frequencies are easier to control then lower frequencies - high freqs can be absorbed by studio foam, lower freqs need more mass. There is something called a slot resonator which someone here can probably explain to you - I can't - which also helps.
Your control room, if you are using nearfield monitors, should be designed to absorb sound behind you, so that sound from your monitors does not bounce back and hit the wrong ear or hit your ears out of phase. Basically, the idea is that you get the sound once, from the monitor and no other times.
You'll also have to think about cooling/heating systems (they need to be quiet and need not to transmit sounds inappropriately) and about lighting and electic (think about it while planning) and about studio wiring (for that, see the thread currently going on in this forum)
For basic construction, build as is suitable for your climate (a floating slab, a concrete base, or full foundations, whatever) and build a largish building using 2x6 studs, insulated with rockwool and with a double layer of soundboard. Inside that, float your floors for the inside rooms on neoprene (rubber) and build secondary 2x6 or 2x4 walls, again with soundboard and rockwool insulation.
After that, it is all details and planning
I'm not an expert, but I read and listen well.... hopefully one of the real experts will chime in, but this ought to give a place for discussion to start from.
