Living In & Running an AirBnb in Japan

We speak with two buyers, one planning to purchase a new/ish Tokyo duplex, the other an old house on a remote island, who are both planning to live at the property and rent it out to short term stay guests via minpaku/ AirBnb. What are the similarities and differences between both of these cases? What special considerations should they keep in mind? How would they each finance the purchase, and what sort of returns can they expect?