Knowing when to call in employees and subcontractors is something that comes from experience and good planning. It also leads to running an efficient operation which will add to your bottom line. Per-inch contracts should also have an ice, removal and stacking clause.
Retainers help you mobilize your operation
Jobs that require an upfront outlay of funds on the part of the contractor justify the use of a retainer. We're talking about things like the purchase of ice melt, placing storage trailers on site, renting equipment, and even having personnel on call. As a contractor, you cannot be expected to take all of the risk and expenses when these types of requirements are placed on you.
In this particular case, you need to work out a pre-arranged sum of money that is either fully or partially guaranteed to you for the expenses involved in mobilizing your operation. It does not matter if you are working on a fixed-sum, per-inch or per-hour basis. You will find that most clients will understand and be more than willing to work something out with you.