Do mechanics liens prevent property owners from taking out a loan? Or does it only affect the selling of the property

A lien does not legally prevent an owner from getting alone, but as a practical matter, can make it very difficult because most lenders insist on clear title before issuing a loan (or permitting drawdowns on existing loans). Unsatisfied liens also affect attempts to sell a property. They generally will need to be cleared (generally, paid or bonded) in order for a buyer to pirchase the property.