I am a Eureka Springs real estate broker/agent. It is my understanding that any home in Eureka can become a duplex with out a problem. When splitting the property beyond that check with city hall regarding the multifamily regulations. As to splitting off a guesthouse to become a separate property the first challeng might be separating the utilities/services. Next, consider if there are lot size issues to deal with. Ususally there are ways to work these things out. I find that the city is on the side of reasonable, informed citizens.