Is the area zoned for you to run a business? If it isn't you'll have to get a zoning variance so that's what I would look into first because without that you can't do anything else. Before going to any expense of a zoning variance however I would do a feasibility study as to whether there would be a market for your retreat. You could check with the Small Business Association (they have a great website too), SCORE (retired executives that help businesses) or a college that has a marketing program. They are often looking for projects to help with classes. Before you invest any money in the business you need to do some research and develop a business plan. Research, Plan and then you can think about twin beds.