I'm off of Long Island, NY. I get a tarp and cover it myself. Two tricks, make sure the peak/pitch is high enough, use wood to make a support ridge and the support poles. The lines from the support beam down to the guard rail can be a good, solid nylon rope, but the trick is make sure the peak/pitch is high enough. Then tie it all down tight. The first year, I bought a blue tarp, which was inexpensive. I covered the boat, trimming the long parts. I used tarp tape to seal the cut edges, and installed my own grommets. The first one is the hardest cause it isn't easy setting the grommets while the cover is on the boat. After that, I used the tarp as a template to lay over a new, thicker tarp. But now I can do the cutting, taping, and grommet setting at home, at my leisure, while its on the ground. Its like making a semi-custom cover for your boat. The thicker tarp is heavier, so it does take two people. But for a fraction of the price, and reuse over a few years, its worth it. I went to www.tarpaflex.com
where I got the tarp, tarp tape, and tarp zipper (two of them makes a door so I can do winter work inside the tarp). Grommets I get from a local hardware store. In the spring, I give it a good rinse, let it dry, then I take it off the boat, store it in my garage, and reuse it the following year.