I have a friend whose father has a lien on his home due to a judgement almost 20 years ago. It was a neighbor dispute and the judgement was rather small, a couple of thousand dollars. The other party has renewed the lien every time it has been due to expire so it is still active (I’m sure my terminology is all wrong, but you get the picture).
He seems to think that the interest is simple and the ammount due now is not too much more than the original ammount. I think it could be much more, multiples of the original sum.
Once more, this is something that can only be answered under the law of the state of the property at issue.
There are two different concepts here, though, the judgment and the lien. First, the judgment is the thing that establishes liability. There is probably a statutory interest rate on the judgment under state law. In New York, the statutory rate on judgments is nine percent.
A judgment lien is a statement on the property records that the judgment exists and that any buyer of the property will be subject to the judgement. A lien may also be foreclosed, which means that the lienholder may start a judicial proceeding (sometimes a non-judicial proceeding) under which the property will be sold at auction and the proceeds given to the lien-holder up to the amount of the lien.
One related question to ask is the statute of limitations on judgements. In New York, it is 20 years. If the statute of limitations is similar in the state at issue (and it may be shorter), the judgement may soon become unenforceable by passage of time.