I have also thought about vacation rentals. Mostly because I have a close friend who has a log home in Maine. He advertises it on one site, Home Away, and always books it for the entire summer. Although last year he has someone leave part way through their stay because of the escape convict that was in Maine. So he lost a couple of weeks rent. He does very good with it. Personally, I believe in order to do it, it needs to be waterfront. Lake, ocean or large pond. Something on Lake Winnipesaukee would be great, if the prices were not so high. But there are many other lakes, I guess. Or oceanfront in Maine such as Bar Harbor would do well, I believe. Key for me would be not having to drive too far. Also, it's a huge advantage if you have someone in the area who can keep an eye on things. By far, the easiest years for my friend was when he had a friend who lived in the town the rental was in. He had someone he could trust to manage the place. It's a bit more difficult for him now, but he still does O.K. He had to find another person in the area to manage it, and although he is pretty good, he is not was good as his friend was. (His friend who had been managing it passed away). He still rents it without problems, it is just a bit more difficult to get needed work done, supervised, etc. I have been thinking about rentals in Newport RI also. That same friend of mine, lives in Newport RI. His neighbor rents out her home for $12k - $14k per month in the summer. It is a great area, close to everything. Close to the Easton's Beach, the Cliff Walk, restaurants, Bellevue Ave, etc.
Key, I believe, for vacation rentals, is to only buy in a great area. Need to have things to do, attractions, etc. I would not even buy in a so-so area. Needs to be a great area. For me, in NH or ME, that means on the water in a good vacation spot.