1.The making of every reasonable effort to perform one’s contractual obligations. Example: A prospective homebuyer signed a sales contract contingent on the sale of her present residence. She is expected to use due diligence in marketing her present house. 2. The making of every reasonable effort to provide accurate, complete information. A study that often precedes the purchase of property, which considers the physical, financial, legal and social characteristics of the property and expected investment performance; the underwriting of a loan or inverstment.