Since it's already Friday, even if you buy the label now, you won't post until Monday and depending on your location and the buyers location, you're looking at 5-8 business days at least, so he won't get it until the week after.

Just be aware of some buyers who ask to have an item shipped later than your handling time and then open a case for Not Received as they will use the later shipping date against you to try and win a case.