Two items to note.
1.) As to what the deposit covers - my question was asking what money has the contractor spent out of his pocket in order to perfrom the work? Again I was talking about about my personal homes that I have built, these are not huge projects so no sub is there more then a week at a time for their given task. If you work the week and I give you a ckeck on Friday, where does the "BANKING" aspect come into play in this senerio, which is what I had described previously. I contend that you don't have to pay for the materials up front, you have 30 days after the 25th of the month. In fact if you pay by the 10th you wll get a 2% cash discount. You don't pay for labor this week, it is generally a week behind, in other words the work you do this week is on next Fridays check. Permits might be applicable in some cases - but around here the City's send you a bill at the end on the month. So I'm not buying the reason for the deposit as being that you have expenses to cover in this senerio. If it's because you don't trust me then say that. Don't say it's because you have expenses to cover becuase I don't think that is really the case.
2.) As to the comment about me only being an employee - so therefore I couldn't possibly understand how things work: My position among other tasks, is to purchase the materials for the projects I manage. In a given year I purchase 1.5 - 2M dollars worth of materials. These are commercial projects, and I guarentee you that you would never get a deposit for a dollar of this materail and you won't see any money for it until 30 - 45 days after the end of the month. Commercial jobs, I would agree, you are acting as a bank.
I hope this post doesn't come across as shouting - that's not my intent.