City considers fourplex a commercial property?

[Billy Bob]

I'm looking at buying a fourplex that's a foreclosure in CA. It's two units downstairs and two upstairs, 2 bedroom each. I would consider it a multi-family property. The City says they consider it a commercial building even though in the past it may have been multi-family. They say that it has to be brought up to current commercial code. Does anyone know the difference between commercial and residential building code in California? What might be required? fire sprinklers? complete re-wire? ADA? seismic upgrades? upgrading fire walls? Thanks in advance! 

[Jared W Smith]

Like @Scott Mac said, find a local architect to review the property, current building and fire codes and what changes are necessary @Billy Bob.