Type of Building Design: Adapting Steel Warehouse (new build) for residential-at home business use.

Structure design: Steel shell with inner wood framing: potential steel beams for selective floor support

Concept: Saving on the framing density of lower floors by supporting the third floor with I beams and by those very beams also frame upon the third floor studs with the entire fourth floor purely of lumber only. Theres not much planned for the 4th flr besides a corporate table and dividing wall. Obviously the first and second floor are also framed in with lumber. Are steel beams capable to carry an entire two residential floors(30x40')? and by what interval/gauge is most reasonable before the material prices up sharply? The third floor will be heavy with kitchen and music studio(3drum kits, amps,etc,etc, piano) (business).