Here in CA, storage requires the use of a bonded warehouse.
Our State laws prohibit the collection of more than $1000, or 10% of the contract total (whichever is the lesser) from the owner on any residential project before the commencement of work.
The GC has to get their money from the owner, and they aren't there to bankroll your job, either.
Setting up your progress payments (as Roger says) is the easiest way to get money soon.
By the same token as the EC not biting off more than they can chew, neither should the supplier. If they want to "middleman" and get their $%, they should be able to bear their share of the burden also.

Virgil, DON'T shut it down. Good to hear from you! Hope alls OK...S