Apple Stores have financing. If you apply in-store and are approved instantly, they can print a barcode and you can buy in-store.
If you apply online and are approved instantly, you can order online.
Otherwise, if they can't verify your credit, or you have been rejected, you probably won't get an answer for up to 2 weeks.
There was a thread I posted in a few weeks ago... search for Credit and you should be able to find it.