If you do this you may lose your purchase altogether.
EBay has an automated (but optional) Unpaid Item Cancellation programme that voids transactions and leaves the buyer with a Strike on his buying account.
Most sellers have automatic blocks against deadbeat bidders with Strikes.
If you attach a credit card to your Paypal account or pay directly with the card, you don't have to worry about waiting for payday. You can pay the seller immediately and pay off the card balance at your leisure.