That $240 a year is a huge deal. I've been there too. There are so many hidden expenses to boating that I never considered, and I had been around boats all my life. The storage shed is always the most difficult to stomach -- because it's the one expense that you really couldn't care less about. But it's completely necessary...
I just moved from an apartment in Seattle, where I had to have the boat in storage. Between the two, my rent was more than I was comfortable with -- but that's the joys of ownership, I learned. The boat was 45 minutes away from the citiy just to make the shed affordable. Still, it was so much more than I expected to spend that I ended up trying to sublet the unit to friends (no such luck -- I ended up with the whole bill).
Anyway, I now live in rural Eastern Washington, in the city of Yakima. My garage door is extra tall, and the garage is extra deep (sort of). While it's a pain in the butt to make the boat fit in the garage, I'm so glad to have it fit. Been meaning to post pics for a while of the boat in the garage. It's tighter than you could ever imagine....
but I don't have to pay for a storage shed anymore!!!

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THREAD HIJACK:
A quick tip on boat storage, for everybody...
In Seattle, the air is very moist for most of the year. But no matter where you're at, I highly recommend investing in one of the simple, round de-humidifiers to put in your boat during the winter. They cost like $50. You'd be amazed at how much moisture they pull from the air when you place them inside your boat cover. There are no moving parts, which means very little risk of fire. But it will add years to your carpet and upholstery.
This is a great, much cheaper alternative to paying for heated storage. If your shed doesn't have a power outlet, you can get an attatchemnt that screws into a light-bulb-socket that accomodates two power outlets and a bulb. That'll save you another $100 a month.
That's what I did anyway....