Neighbor erecting fence on boardering driveway,my house for sale, will devaluate my home & restrict my drive, can I sue?

There are two issues primary which are important when fences are installed: First does the local zoning permit the installation of a fence where it is being installed? and Second, is it on his property? You didn't mention where you live.  Many cities have zoning ordinances that prohibit fences in certain areas of your property.  I am in the Cleveland area.  I know of at least one local municipality that prohibits fences forward of the back line of the the home.  Too close to a drive might be another issue or too close to a road.  Check with your city to determine if there are any such restrictions.  Don't take it for granted that there aren't restrictions just because you see fences in the city.  It may be in a differently zoned area or the fences may be in violation of the zoning code.  If it is a violation, the city should enforce the code and force the fence to be moved. You shouldn't assume that the fence is actually on your neighbors property or where the property line actually is for that matter.  Unless you can find a surveyor's monument, a monument that you can be confident of, and can use it to determine your property line with some accuracy, you will likely need to hire a surveyor to locate the property line.  Surveying is a real skill that required calibrated instruments to be correct, so although they might seem a little pricey, unless you are POSITIVE about the property line (not just what you were told when you bought it) it may be worth paying a few hundred dollars to satisfy yourself. These kinds of disputes are actually pretty common.  I teach a class in Mediation at Cleveland-Marshall College of Law.  The first mediation that we do is a property line dispute. You say that your home is listed for $85,000 and tax appraised for $91,400.  Tax appraisals, particularly in this volatile real estate market are notoriously bad, perhaps reflecting your original purchase price.  Real estate agents often tell owners what they want to hear about a listing price to get the listing.  It's likely that you didn't expect to sell the home for $85,000, but had that as your starting price.  Consider the $60,000 as an offer.  Don't be insulted, but do what you would do with any other offer, counter-offer.  Who knows, you might be able to come to a price that you are both happy with, remember, though, it is still listed and you will likely have to pay a realtor commission, even though the realtor didn't bring the neighbor to you as a buyer.