Carolina Carport, 18'x32'. Cost me about $2400 installed, but keeps the rain, sun, snow, leaves and bird poop off my roof. We bought it 6 years ago, have at least another 8 in this house. That's 14 years, or $171 a year to keep it under cover and dry. That's cheaper than buying a cheapo cover every year, far easier and more effective to use.
Our next house will be even cheaper per year, because we'll be there for a lot longer. Consider it if you can. Its a small investment (10% of the price of my new camper in 2015) that keeps my trailer looking newer longer.