My cousin did something like that, he had to move so he bought a lot, built a garage with a second floor, he had his kitchen/livingroom on the ground level. That gave him a place to live in right next to the house he was building. Once the house was finished he moved his stuff and now has a sweet heated garage with loads of storage space on the second floor.

In his case he had to build a temporary wall inside to enclose the garage door because of winters.