How do I provide a quote to a customer for exterior painting job?

By the Sq. ft. and there is probably a rate painters in your area charge plus or minus a few bucks that and the cost of materials ie. paint and supplies. but if your not licensed and bonded than you cant charge more than your area contractors laws allow where I'm at it's no more than $300.00 a job so i split it into more than one job like 300 for primer 300 for painting exterior 300 for exterior trim