I made an offer and the seller REJECTED!

I found a property in a great neighborhood that needs tons of work. I mean at least 75-80k. The seller is acting on behalf of his mother. The property has been vacant and in unlivable condition since at least 2009, maybe before then. Long story short I did my calculation to get my MAO and it was rejected. I have room to increase my offer, however the work I've put in to find this property, the amount of phone tag that's taken place kind of makes me question whether or not I should do business with this guy. He's a used car salesman so he's been talking a good game and since I'm a newbie at this he's really getting to me. Raising my offer seems like it's the only way I could possibly get this house under contract. How does one deal with a rejected offer?