Due diligence within real estate transactions refers to both the buyer and seller satisfying various aspects of a purchase contract before finalizing things. The inspection period is typically a 10 calendar day window provided to the buyer to research important facts and perform a physical inspection.We provide you with a FULL guide to help you find the answers to all your questions you may possibly have about your new home. The Arizona REALTORS® Residential Resale Purchase Contract Due Diligence Section: Inspection Period and Buyer Disapproval. In this report a careful inspection of title and physical condition of the premises is done before the transaction is completed. Due diligence is a critical process in real estate that involves researching and verifying information about a property before making a purchase. What should be on my due diligence checklist for real estate purchases?