Other Trading/Upgrade at apple store

[dslrjunky]

so this will be my first time trading in a device to do an upgrade. I was hoping I could do my upgrade/trade in at an apple store. Does the trade-in applies as month-to-month bill credit (i read somewhere with apple it's an up front credit, but want to be sure). also if I do the transaction with device trade-in using the app store and in-store pick up is it possible for me to add a downpayment on top of the device credit to lower the monthly payment? I hope I didn't confused anyone.