I do smaller jobs, anywhere from 125.00 to 10,000.00, I like to ask for a deposit on jobs outside my funding capability when usually supplies are over 1000.00. Another reason I ask for a deposit is it essentially locks in the estimate showing they agree with the terms, to do a large job upfront with no deposit gives the client to much control. ... just sharing my world.
Also if I do a job for 3-4 weeks, I'll usually bill up to date per week.