There are at least three different basic types of steel buildings, which type might you be looking to buy?
Typical steel construction using C channel, Z purlings and girts, steel sheet, some welded steel trusses.
or, carport like structure made from galvanized square steel tubing,
or the corrugated steel building with no structure, the steel skin IS the structure, many times built in Quonset style building.
And yes, as noted before, how many doors, what type of doors, windows, etc.
Charles