To start with you need a lot of money, between $150,000 and $200,000 USD in my case. Most studios are built within an existing structure, ideally something double-skinned, made of brick or concrete block with a solid floor. Unless the studio is a long way from other dwellings it needs to be soundproof which means you need to create mass to block airborne sound, around 100dB in my case. Building an airtight room within a room is the way to achieve it, doing away with windows and as many doors as possible as they will always be a weak point.
You need a lot of kit for AC power handling including surge suppressors, noise filters and other stuff plus everything like switches, sockets and lighting etc needs to be surface mounted to avoid creating sound leaks. A digital air con or some form of air conditioning is also pretty essential. The other big consideration is how the room sounds which means employing various kinds of acoustic panelling and bass traps.
I've already have most of the recording equipment required including a 128 channel mixing desk and four studio rack mounts full of various equipment so once the building work is completed I'll be almost ready to go.
