500 sq ft of floor space in attic

This post-frame garage measures 30x40 with 10ft ceiling on ground floor and 500 sq. ft. of attic space on the 2nd floor. 

Features:
- vinyl siding and asphalt shingle roof steep slope (8/12) roof 
- attic with full size stair case leading to 2nd floor         -two 9x8 garage doors