How to value this property accurately

[John S Lewis]

If there are any appraisers out there, hope you can chime in.  I bought a mixed use property that really, legally was not a mixed use.  Was commercial.  I've since gotten a use variance and I'm turning the property into a duplex.  Would a bank appraiser be looking at this as a residential duplex or a commercial property?  Does it matter?  I'm trying to determine valuation, and good comps are few and far between.  It's also pertinent, because, at least here in NJ, the basement was counted as gross sq ft because it was commercial .  If it was residential, it would not be included in sq ft.  

Does the process of separating the building from 1 mechanical service system (heat, hw, elec, etc.) to two separate metered units add value to this building?  If yes, how much?

Finally, anyone have any input as to the value of the use variance? Seems to me it's a fairly powerful tool.