Wow. I am really surprised to learn you guys are demanding, and getting, money down, especially from a GC prior to starting work.
Although I haven't hired much done on a resi level in my life, I have never been asked for money down nor would I agree to pay it if I were. I would find a different contractor.
That goes for plumbing, concrete, siding, roofing, gutters whatever.
Asking for 50% down would send a big red flag to me telling me the contractor isn't credit worthy and is a risk to me, the man about spend his hard earned cash on you.
I understand the "I am not a bank" mentality but still, why would you need to be? Let the supply house be the bank. You get the same price if you pay within 30 days, minimum maybe longer, and maybe a 1 or 2% discount if you pay within 10 days depending on how credit worthy you are and what supply house you're dealing with.
I don't know if box stores offer these terms as I try not to deal with them preferring real supply houses instead. Yes, they can be competitive with the box stores and the support is waaaaaay better.
Learn something new every day.
BTW - I don't mean to imply those of you who are demanding money down are not credit worthy. I am just surprised that this policy is so prevalent. I know for sure if I got a $1,000,000+ commercial/industrial/healthcare electrical project and asked the GC for 50% down, or any amount down, they would probably hang up the phone and immediately dial the next bidder.