If you're asking how long a buyer has to pay for their purchase, the amount of time is set by the seller. Some require immediate payment, some allow 4 days and others allow longer.

I have found that allowing 7 days works best for me, but different strokes for different folks.

If you are asking how long it takes for the proceeds of a sale to hit your bank account... again, the seller sets the payout frequency. It generally takes between 2 and 6 hours for my payouts to appear in my bank account.

Just remember that only funds which have completed processing will be sent to your bank account. Funds on hold will NOT be included in your payout.

After 4 days, cancel the order using the reason "buyer hasn't paid".

https://www.ebay.com.au/help/selling/selling-getting-paid/buyer-hasnt-paid-open-unpaid-item-case?id=4137

Then block the buyer  if  they've made no effort to contact you.... and relist

A buyer has 4 days to pay, if they don't then you can open an unpaid item dispute.

Note that as a new seller you money will be on hold for up to 30 days anyway.