If you require a garage, this will be built on-site, separate to the install of the project modules. This can increase on-site times and can be built either before or after install of the main house.
Have you thought about a connection from the garage into the main house? Will this be through an intermittent space, such as the laundry, or straight into the main home? These decisions will influence the overall layout of the home, and require careful consideration.