2005 Outback H6 motor leaks oil from passenger side, should I buy?

[tpdtopcop]

Hi guys just as the title says. The guy that has it listed as a 2.5ltr and I was shocked when I popped the hood and the H6 was staring me in the face, however when I looked underneath there was a oil leak or oil coming from the passenger side by half shaft area. I really want this car but afraid of leak. What is the probability that its the valve cover, oil pump O ring or the oil pressure sensor? I guess that's what mostly or could be the cause. If any of those how hard is to fix?

Thanks