@Linkasink Should be as simple as using a Current Asset as the detail line on the 50% deposit check you are creating for the Vendor.
Per your example, this will cause $500.00 to move from the relevant bank account to the asset.
When you go to pay the remainder of the bill to the customer, create another check, but use -$500.00 on a detail line for the current asset.
This will allow you to then enter the full $1,000 on a second detail line for whichever account you're using to track inventory, reducing the amount coming out of your bank account for the second check to $500.
Total of $1,000 comes out of the checking account, $500 of which was briefly tied up in a current asset. Current asset gets lowered to $0, and you end up with the $1,000 in inventory.
