Marian, There are people that need this type of property but they may be hard to find without a lot of marketing. Where do you have your home advertised? Are you advertising in the local paper? Online?
Do you know what this property would rent for in today's market? What would the house rent for and what would the inlaw suite rent for? This may be best suited for an investor that could have two rental units on one property. Can you give me more details about it?
I understand you don't want to use a realtor and I respect that. I just need more info before I can really give you a good answer.
It doesn't matter what you can prove. If the buyer bought the property at an auction and probably got it under market value, he can set any price he thinks he can get for it as the price to sell it for. You can also offer him whatever you feel the property is worth. Either he will accept, reject or counter on your offer.
Have you looked to see what property in the area sells for. If most homes sell for $100,000 and you pay what he is asking or say $70,000 and have to put $20,000 into the property to get into good shape, you are still $10,000 ahead in property value.... more