It has become customary for sellers to be responsible for Title V for a simple reason; most banks won't lend on a property with a failed system. So when we see "buyer responsibility" what it really means is "hard to borrow money against". As you can imagine, that significantly reduces the number of people who can purchase the property, so I often find that these properties sell for 30-50K below market. Most people who purchase have done a septic replacement before, and understand the in and outs, and that's a good thing - the process, while not overly complicated, is confusing to newbies, and is time consuming, expensive, and often involves a great deal of red tape.
Matt Heisler is a real-estate professional and owner of Heisler & Mattson Properties. He has been selling residential real-estate for over 10 years. He has given several talks on real estate, including presentations on first-time buyer tips & tricks, and profiting in real estate investing in Massachusetts. As a Vanderbilt University alumnus, he is proud to serve the communities of Natick, Framingham, Medfield, Millis, Holliston, Hopkinton, Southborough, Westborough, Northborough, Grafton, Marlborough, Shrewsbury, Worcester, Milford, Charlton, Northbridge, Sutton, Hudson, Sudbury, , Clinton, Boylston, and West Boylston. His company website can be found at http://www.bjheisler.com, and his Metrowest Blog can be read at http://HomeSellingInMass.net.
Hope that helps,