You said you were going to look at your numbers. What numbers do you have?
Assessed value is a terrible measure of real value. Obviously, rumor is too. I wouldn't trust anything the seller says is the "lowest" they can go. If you trust that, I have a lot of properties I could sell you!
So, how are you going to gauge what it is worth? If you cannot answer that question (on any property) you should not make an offer on it.