How do I enter and receive a line item on a PO with zero cost.

You can make it a penny, and then when you receive and cost is, just cost it at zero, when sending over to a/p, it will come up as zero at the top of the a/p, your distribution lines at the lower part of the a/p record have to have value, at this point, you would put a penny into the first distribution like, then create a 2nd one to match the same codes as the first and make it for a negative penny, then save the a/p and go void it. This now shows your inventory with zero cost.