I've order many cars. A new dealer who does not know me may ask for $500 or $1000. The ones who I have bought from before never ask.
They may ask for down payment if you try to order something odd that they feel would be hard to sell however. Back in 1980, I ordered a fully loaded Silverado with a 3-on the tree. That was a $500 down, first time dealer. I can understand.
My current dealer has let me order my second 2019 Limited (black and silver). Both loaded, neither shipped yet, allowing me to accept the black or wait for the silver. Neither required anything down. I think sales to a customer takes priority over one speculated for the lot. Both my orders were eTorque & ramboxes, making dealer happy to get one for selling to someone else.