So, basically, you are buying a car from someone who needed to finance it, then wants to sell it before the term of finance is up. To me, you are dealing with someone who isn't the best planner or the most financially responsible. I would contact the lien holder directly, pay off that amount directly, then pay the difference to the seller.
2014 Audi S6 * 2015 Audi S3 * 2015 Porsche Cayman GTS
Former 2011 BMW M3 owner