I would be best to keep it in closed storage. i have a 15X30 storage unit 3 miles from the lake. I pay $90.00 a month and it's a brand new unit. I also have a slip with a lift that has screens all the way around the 12 slips that are in my group so you can't see my boat when the screens are down and it's $185.00 a month. It sounds like where you are is way to high. I might understand if you were in California but it looks like you're in NC. Prices should be close to TN which is where I am.
In my opinion nothing wears a boat out faster than storing it outside! My first question when buying a boat is has it been stored inside or outside? If they say outside I move on.