Being born and brought on the beach, and my folks having rental units (that us kids had to clean), all of the basement units had concrete floors and all of the upper units had lino. My folks would replace the lino when it wore out because the sand would eat away the floor. My dad said, it was just a cost of being in business and it was figured into the rents.
Now, my experiance as a Building Inspector at the beach would lead me to use a light colored 12" semi rough tile. I would use a sealer at the start of every season or so, depending on the wear.
I have seen people that have spent alot of money on hard wood and regreted it. Sand an wood just don't go together! I know a guy that applied several coats of sealer to his hard wood floor only to redo it because it was too slipery to walk on.
Concrete where you can, tile the rest.
Note* Unless you have experiance with rental property, I would recommend that if this is going to be a summer rental (big rents), keep it that way! don't turn it into a winter rental until you can afford to lose one summer season's rent. (When the tenants don't move out!)