When working with a contractor, don't make final payment or sign an affidavit of final release until you are satisfied with the work and know that subcontractors and suppliers have been paid. State lien laws may allow unpaid subcontractors and/or unpaid suppliers to attach your home.
When buying a house, be sure to change the locks immediately. There is no telling how many people had access to the previous owner’s keys. When renting, be sure to ask about the landlord’s key-control policies.