Take 5 $100 bill with you. If the motor turns over and he has a title, offer that. If he won't accept it, walk away. If it was worth $1,300 5 years ago when he bought it, and now its sat, you'll be spending at least $500 more to fix it and get it running right. That puts your investment at $1,000, all its probably worth anyway.
I would bet that upon close examination there's tons "wrong" with the bike and he or other previous owners have modified, butchered, or buggered electrical, carbs, and suspension bits. Expect it needs a battery straight away, probably a full brake rebuild, likely front fork seals, maybe fork uppers, shocks, tires, carbs rebuilt, and electrical gone through and corrected. If your buddy is fully up for that, then pay the $500. Seller probably wants it "gone" and cash in hand is worth a great deal.