Tarp is a bad idea, it can trap moisture inside. $40K building is probably very nice. I bought a $2400 installed carport from
Storage Buildings, Garages, Carports, Horse Barns & Gazebo Kits . Best money I every spent.
Keeps rain and snow off the roof, keeps leaves and sticks off the roof, easy to drive under and drive away from. No climbing on/off the roof, no storing a wet/dirty cover.
Allows me to keep window's open year round to prevent moisture buildup. Allows me easy access to load and unload, even in poor weather.