Hyphens are good for search engines...
You will notice nearly every blog/news site uses hyphens in the url plug to boost the SEO
The .net owner may give you $500. I would approach him first for a quick sale of low $xxx. Perhaps just call him and let him know you're liquidating domains and want to offer your .com for a reasonable price.
Otherwise a domainer would pay reg free to $25 and then they would try to sell it to him - or possibly put an adsense site on it.
You may achieve nice passive revenue with a simple website, some blogs and helpful resources. especially if it receives natural traffic - which it might. You could promote it for free in the vacation rental section of craigslist.
Does it receive traffic?
The domain could become a niche specific resource for people searching for vacation rentals in Hawaii - which is a steady market.
Or...it could be used more towards the real estate buyers niche - which you could probably find some scripts to plug in to the site to show current listings.
Or...you could turn it into a website that could be targeted towards home rentals for both the renter and owner. There are always people searching for rentals.