We just had a 41x20 Metal RV Port built last week. It is the classic style with enclosed back and an extra 3 feet down the sides. Cost was about $4800. The company we bought it from provided the engineering plans because I was required to get a permit. Another company wanted to charge alot more for a certified kit.
Ours is rated 110mph and bolted to concrete slab. I had to have the pad poured first. These guys came right out and put it up in 5 hours on time and did good work..
Check your city and county for permits and restrictions...Just because you have room does not mean they will let you put up a cover..
Pacific Metal Buildings