Would you hire an appraiser?

[S R Scearp]

Last weekend I looked at a duplex that is not on the market yet. This will be an owner-occupied building as I need a place to live. The asking price makes financial sense but as an investment obviously I'm looking for the best price possible. Here are some details:

City's "full market value": $97K
Asking price: $120K (this is typical for a duplex of this size in this area)
Zillow estimate: $134K (seems high given the local market)

The property was purchased 4 years ago as a foreclosure for $80K and has been extensively renovated and modified- on the interior only. The inside needs absolutely nothing as it was stripped to the studs and has all new insulation, doors, windows, sheetrock, most plumbing and almost all electrical. Genuine hardwood floors (not laminates) were installed in most of the downstairs and half the upper apartment. Downstairs kitchen is completely new. All appliances are no more than 4 years old (washer and dryer included in sale)

The outside is a different story: the porch needs extensive work, I need to have the roof structure inspected (the slate itself seems fine, and there are no water leaks evident). And the siding- needs to be removed and replaced over the entire structure.

The owners claim all the interior work done has only raised the assessment by about $8K to its current level.

I like the house, but really feel I need an expert opinion on its market value before negotiating with the owners on the price. Should I hire an appraiser? What would you do?

On a side note, since there is no realtors involved, is it fair to offer less by half (or more) of what the commission would've been had realtors been involved? Should I have the roof inspected before or after making an offer? Should I get an estimate from a contractor for siding replacement before making an offer?

Thanks for any input.