If you're building a new garage and have the space available on your property, consider making that garage large enough to accommodate all your vehicles. While the initial investment will be higher, you'll ultimately save a great deal of money in rental fees.
For a superior carport design, also consider the following: When building a wood carport, make sure the type timber used is suitable for exterior applications, as well as in-ground applications when making posts. Carport height is important; 7-feet from the finished ground to the underside of the lowest end rafter is standard. The roof fall or slope, should be at least 2-inches; slope should be steeper (about 6-inches) if using clear PVC for the roof so water run-off is faster and roof stays cleaner. A carport size of 20-feet by 10-feet is modest; construct yours bigger if the vehicle (or boat, etc.) you are building it for is large, or if you plan on using it for other purposes in addition to vehicle shelter. For instance, as a place to sit and relax, or to work on hobbies and make repairs, etc. Posts set into the ground in concrete and bolted to the beams (using two bolts at each meeting) usually do not require further bracing. Posts supported by galvanized post brackets alone will require additional bracing for increased stability.
A 2-minute hailstorm can cause cracked windows and headlights, and create surface damaging dents and dings to unprotected vehicles that not only mar the appearance. But break down protective finishes; an open invitation for rust and peeling paint, causing further damage.
However, don't make the mistake of thinking that a garage is your only option. If your property can't accommodate even a small garage, building a carport is still a great way to protect your vehicle from the elements.