You really ought not to be bidding if you are not in a position to pay promptly. No matter, just so you know, - you have 4 days after the auction ends in which to pay if only because a seller cannot file an Unpaid Item dispute against you any earlier.
Once that happens you have a further 4 days to pay, after which without payment you will get an unpaid strike on your record. A strike lasts 12 months. Most sellers have autoblocks against people with strikes, so avoid them if you can.
If there is to be a delay in payment for any reason, be sure to contact the seller right away to kindly explain your situation. It's bad manners to leave a seller in the dark. And for your own reference, have a look over this link about Unpaid Items:
http://pages.ebay.ca/help/buy/questions/unpaid-item.html
