What should I charge per SQFT to draft in AutoCAD any particular project including sign&seal from architect.?

IM A CAD DRAFTER . MY FRIEND & I ARE GONNA TRY TO START A COMPANY. SO IN THE MEANWHILE WE WILL BE DOING SIDE JOBS LIKE HOME EXTENSIONS , SMALL RESIDENTIAL AND RETAIL PROJECTS, AND ALREADY HAVE AN ENGINEER TO CHECK, SIGN AND SEAL DWGS. SO I JUST WANTED TO GET SOME IDEAS ON HOW MUCH SHOULD I CHARGE PER SQUARE FEET ON A PROJECT. OR WHICH OTHER WAY I CAN CHARGE PEOPLE.