They can definitely be profitable. I've been renting vacation homes in northern Michigan for 8 years with great success (compared to any long-term rental that I've ever owned). However, the first couple of years for each property, are not profitable, as there are several start-up costs to make up for over time.
Each of my properties is different from the next. What I have found to be the most appealing to customers is a blend of aesthetics and amenities. For example, all of my places are lake front. However, I have a property that out performs the others because of it's new, but rustic (knotty pine) interior and furniture. In addition, it's beach and crystal clear water. I operate a second lake house, directly across the lake from it. It is more modern (drywalled), larger than my other homes, and it it only brings in about 75% of what my top performer does.
I earn enough over a 3-month summer rental season (June-Aug) to cover all of my annual costs. Anything above and beyond is profit. I know what the annual sum of my debt service, utilities, maintenance, cleaning, etc is. I rent by the week during the peak season, so I divide those costs by 12 weeks, which determines my rent and cleaning fees to achieve my break-even point. Determine the length of your profitable rental period and do the same calcs. Every booking beyond that season is your profit. If the rental fees don't comp to others nearby, move on to another location and property that does. Remember that dealing with expensive properties equals high carrying costs while they sit vacant.