What does it take to build a garage
Wood plywood rebar cement and time and most importantly a good foundation to tie into
It takes building materials, garage kits and accessories and in addition the contactor who will be able to build it. Check out http://www.fixr.com/costs/build-attached-garage for the breakdown facts.
most important is water proof shelter
It will take a professional.
Engineered plans. Don't fool around with jury rigged, homemade, construction solutions. The amount of weight you will be dealing with necessitates a well thought out plan that won't end with you or someone else lying under a pile of rubble.