A lien is any legal claim on a real property that functions as a security for the payment of a debt or any other financial obligation. If the debt is not repaid as agreed upon, the lender (lien holder) can foreclose their claim on the property and force a public sale of the property to repay the debt. The most common type of lien is a mortgage. Liens also occur as judgments against the property owner and from recent unpaid improvements to the property, unpaid taxes, and unpaid utilities. One thing a real estate attorney will do for you is to investigate whether there are any outstanding liens on the property at the time of the transaction closing.