This modern ADU house plan gives you a 644 square feet apartment set above a 3-car 990 square foot garage.
A 10' by 8' overhead garage door accesses the left bay which extends all the way to the back wall while a 18' by 8' overhead garage door opens for the 2-car bay. 
A sink and workbench line the back of the garage and there's storage under the stairs.
A man door on the back-right corner takes you to the apartment with a bed and bath on the right and a living room and kitchen open to each other on the left.