How long will it take for my brand new domain to start resolving?

Max. time for a brand new domain to become accessible worldwide:
48 hours.

New registrations can take a while to propagate out through DNS, although usually most name servers will see the new domain within a few hours. Porkbun informs the appropriate registry of your new domain immediately, but it can take some time before the registry makes that information public. This may be why your recently-purchased domain might not receive web requests or emails for some hours after registration. In practice, most domains are accessible within a few hours of purchase to most of the Internet.