Find a professional Realtor to help you. I have found Zillow to be unreliable at best. They take a grouping of data to value a given property and most often it's a "miss". Find someone to pull some comps for you on recently sold similar properties in that area. Then you will have a better idea of the real value of the property and be able to make a reasonable and educated offer. Websites that offer values on homes aren't reliable. You don't know what they base their information on and there are so many factors to be taken into account.