Investing in Beachfront Property

[Charles A. Armistead]

I own a single-family rental in North Carolina. I am new to investing in property but would like to invest in beachfront property. The purpose of the property would be to place on Air Bnb and like websites for short term use. What are investors' experiences with these properties and what are some less obvious criteria to consider when purchasing a beachfront property? Some criteria I believe to be true or is unclear are below, please correct 

1. Monthly income on rental should be 2x monthly mortgage. 

2. Expect to pay property manager 10% of the monthly mortgage. 

3. What are the average costs of cleaning companies? 

4. What is the average monthly cost of insurance on beachfront property.

Finally, what have been your experiences with these properties? I have one friend who has already invested in beachfront property and swears by it.