There are too many intangibles to answer your question, talk to your realtor, or get one.
An appraiser looks at closed properties and looks at past sale history so you will know what's too high and what's the low, so you will be in the range.
A good realtor will negotiate and articulate a good argument that will help you make the history upon which other properties will be appraised at.

Largely depends on many variables.

Condition, exact location, floor, assessments, upgrades, parking, etc...

Consult with a Realtor or appraiser for help with this.

You will need to look at recent comparables as a guide. I is difficult to believe that Zillow will be able to weight the above mentioned factors perfectly. If so, every mortgage bank and investor in the country would have them retained.

Best of luck with the deal.

As,

Listen to me on this one. No disrespect to Tom. Do not search for values on Zillow. They are more likely than not wrong in some shape or fashion. The only person..... Listen to me..... The only person that should be giving you an opinion of value is an appraiser. I know the realtors on here are going to disagree but trust me. I am a mortgage broker. I deal with the actual loans on the property.

I can have an actual appraiser do a comparable property value search for you at no cost. Give me a call when you get a chance.

Sean Cochran
Quality Mortgage Lending
630-330-2229

As,

If you were my client I would avail you of a spectrum of services that include tangibles such as comps and a decade's experience and expertise in the Chicago market. I also would bring to the table on your behalf intangibles such as intuitive market knowledge and anecdotal awareness related to specific buildings, general locations and overall neighborhoods. This question is best posed to the real estate professional you have chosen to work with.

If you are not represented by a real estate professional I am puzzled by the fact that you made the conscious decision to not rely on a realtor but now as you reach the crux of your search - the written offer and its subsequent negotiation - you turn to real estate professionals for their input. That seems ironic.

With respect to your question pertaining to value - I hear that zillow provides a host of services, including comps.

Best of luck!

Tom McCarey
The Real Estate Lounge Chicago