Cheap studio build question

[bpence310]

What would be the cheapest way to retrofit a 25x30 spray foam insulated metal building with concrete floor to have decent studio quality? I do have metalworking tools (lathe, mill, etc) in it, as well, so I would like to keep it to about half of that space, if possible. I am not looking for like high-end quality, but decent would be nice. I would like to be able to have my drum kit, rack, room for a guitar player or two and vocals be able to play together and not have it sound like trash. I am not opposed to the "building within a building" method, but I would like to do this on the cheap. I have a 20x40 building with a dirt floor and have considered doing that method inside of it, but I'd like to see what options I have that would be acceptable, rather than perfect.