Final answer:
An Oregon principal broker can only pay a listing finder's fee if the finder is a licensed real estate agent, irrespective of the property's sale timing, the finder's relation to the buyer, or family connections to the seller.
Step-by-step explanation:
In the context of Oregon real estate regulations, a principal broker may only pay a finder's fee to someone who has helped to identify a prospective property for listing under certain conditions. Specifically, the key condition for paying a finder's fee is that the listing finder must be a licensed real estate agent. None of the other scenarios mentioned (property sold within 30 days, listing finder being the buyer, or being a family member of the seller) are relevant to the legitimacy of paying a finder's fee. It's important to ensure compliance with state real estate regulations to avoid any legal issues.