Believe it or not, I’ve known some property owners who make it a point not to seriously consider offers from attorneys.
Asking the question “Can I get away with it?” is different from “Is it right to do this?”
Renegotiating to deal with a problem that has suddenly come to light is one thing – timing it to take maximum advantage of a seller after the deal has already been struck is another.
You’d be ready to go to war if a contractor or a car salesman did this to you. If you don’t like the deal I think you should just back out.