A good way to judge your potential "income" and rental rates is to research your existing competition and other people currently listing on Craigslist or other listing site.
In Hawaii, it's brutal as very nice condos are presently renting for $89-125-200 a night. Condos there have insane HOA maintenance dues of $500-700 A MONTH.
a GLUT of condo's on the market for sale or rent makes it upside down for a potential buyer/investor, even when today you can buy a for sale $200-300K condo that was listed 3-4 years ago at $500K.
I simply don't get the super high maintenance fees.
but a couple links for you.
Hawaii Kona Real Estate KonaListings.com - Kona Hawaii Real Estate for Sale
big island vacation rentals classifieds - craigslist