in order to soundproof a space, you essentially need to either create or modify existing walls keeping a few things in mind: To prevent sound from escaping the space, you essentially need to put into place heavy walls. The more dense material used for the walls, the less it will vibrate and less sound will pass through it. In addition, products like Green Glue provide a dampening layer that absorbs a lot of the sound.
Most walls are built with a hollow framework and either faced with drywall or sheetrock. The wood frame as well as the airspace allows sound vibrations to travel very easily. In order to reduce the noise passing through the wall you would build instead with a layer of pink foam filling the airspace in the wall frame, and hang thick sheetrock, then sandwich another layer of the same material on top of a layer of green glue or other dampening agent.
Since we're probably going to be building a recording booth, this will allow us tp construct the best walls given the situation. In terms of flooring, I believe the best soundproofing you can accomplish is pouring a slab of barium-loaded concrete for the foundation of the space. If we could do this then we would have 0% worries ever in a hundred years.
the idea for floors is really the same. Put in place a massive stable layer and no vibration will pass though it. there are products available that we could easily install on the floor of the space, most of them a form of mass-loaded vinyl sheet.
another benefit to building a studio inside an existing space is that if the studio room is in no way mechanically connected to the outside room, then we've solved a good bit of our soundproofing needs by not allowing the vibrations to transmit outside of our studio. Once we have a space, then we can design a room to build inside it that will be our recording studio. It will have to be large enough to house our dj booth as well as our live performance space. It must have no parallel walls - these create standing waves that can ruin the acoustic quality of the room. Since I think it's better to do something well or not at all, this could be expensive.
I'll keep you updated