I do not recommend leaving them natural. They should be cleaned and have a couple of coats of clear stain or acrylic sealer applied to keep the dust and dirt out of the wood fiber. Makes it much easier clean the logs also. Tell your Realtor to stick to selling! 80% – 90% of log homes are sealed on the interior.
Call Dave at Timeless Wood Care Products for help with what exactly to do and what to use. 800-564-2987