I'm an Arizona resident and recently started renovating my property using a general contractor. In the contract we agreed to specific payment terms (20%, 10%, 30%, 30%, and 10% after completion). At this stage of the project, we've paid a total of 30%. We used a general contractor to manage the project so that scheduling, purchasing of materials, and payment of the employees would be managed. Recently, one of the GC's subcontractors contacted us directly and mentioned that if he does not receive payment for his work, he will place a lien on the property. How can I protect myself from this?