I want to sell on ebay, do i have to pay for the auction before it goes up for bids? or once the auctions over

I want to sell on ebay, do i have to pay for the auction before it goes up for bids? or once the auctions over? id much rather pay them by pay pal but i have to wait for money to be in my account in order to pay them and no i dont wnat to put money in there myself!!! i want to use the money that i sell to do that