AP down Payment

Hello,

can someone please explain to the process of AP down payment.

here is my situation: we get a PO for 50,000 but the vendor requires 50% so they send us an invoice for just the 50% (25,000). I would like to know what is the best steps to  posting a down payment......do I use f-48 to post the payment first then post the invoice. if I use f-48 how do I print out the check, the vendor want the check to have the invoice. keeping in mind we would get another invoice from the vendor for the balance.