Having a detailed garage plan is a prerequisite for anyone building a garage -- pro or do-it-yourselfer -- because it's needed to get a local building permit.
You don't have to spend a bunch of money to have a plan drawn up. Lumber yards and mail order services sell a range of plans.
However, if you plan to closely match your house or want some custom features, consider hiring a draftsman to tailor your plans. Our garage plan was purchased from a design service for about $50.
A garage kit is a general term that refers to a model kit that has been manufactured in a small facility such as a garage or similar building at home usually employing only a handful of people at the most. These kits are sculpted, then molds are made and finally castings are poured. These kits are not mass produced so they are relatively hard to obtain and since they have low production runs they also have relatively high price tags.