Start with a Comprehensive Garage Building Plan
The very first thing you need to do in the process of your garage build is to establish your goals and make plans to achieve them. Decide about the size and purposes that your garage will serve. Also ask yourself whether you intend for the garage to always remain as a garage, or will you perhaps want to convert it to a living space down the line?
Will it be one story or two? Will it only be a vehicle storage zone, or will it need to be more? Keep in mind that if you decide to include things like a workshop in your garage, you will likely also need to add insulation, heating and air so that you will be comfortable while in your garage.
Decide what your needs are and take them to an architect to have plans drawn up so that you will be better equipped to estimate the costs of your garage construction project.