What are the numbers on east coast beach homes?

[Chase Cannon]

I have been looking into adding a vacation rental on the east cost (NC, MD, NJ) to diversify my existing properties. After looking at some of the sell prices as well as the weekly rental prices offered May-Sept vacation timeframe, I am wondering if anyone is willing to share their experiences on the finance side of their investments. Clearly, there must be a vacany rate issue in the winter months (I assume). However, some of the prices I have seen based on an assumed 25% downpayment on the 30yr fixed (minus in cap exp.) seem to make the RoR reasonable enough to consider. Any details (good or bad) that they wish to share would be much appreciated. 

Thanks.