Property Tax Lien I doubt he'd have anything like that.
IRS tax lien then yes. court judgment he'll have to pay it. The new homeowner recvd a title insurance policy but your friend was cleared to sell the property. Look on the old hud sheet it may been paid at settlement in 2004. but Judgments and IRS state Tax will follow him.
Did he look to see if was paid at settlement? if it wasn't paid at settlement what type of lien is it. If its his debt he'll have to pay for it. Any liens were paid for at settlement back in 2004. It could be something that never was reported as paid at that time. Just a little extra work that's all. I hope that is all it is.
Ask to see the title and what the lien is then re ask here.