What does your Realtor say?
You have some great advice here, what you really need is someone that has seen this property, also knows the local market values and trends. Are values going up or done? What have comparable homes sold for recently?
Your Realtor's job is to take the mystery and uncertainty out of purchasing a home. If you do not have one, then find a competent Realtor. They will save you time, money, and stress.