Tobacco Road, while not exactly a resort, gets by fairly well with only one golf course and no members. I think the key to survival is the location of the course. If the location is very remote, and there are no other options, or very few other options, more than one course is likely needed, unless you have something unbelievable. On the other hand, if you have a resort in a 'resort' town, like Pinehurst, Myrtle Beach, Monterey, etc. you can get by with one course and a good hotel. Shadow Creek also has done well as a single resort/casino course.