Usually they start on a plane like Cessna 152 that is older hab their parents. Even military pilots start like that, just tend to switch for newer turboprops sooner.

For reference - considerable portion (possibly even majority, especially if you don't count USA due to different licensing) of airline pilots will have their first jet/turboprop experience when they will be training on airliner after getting their "frozen ATPL". In one airline it was common for chief of training to give every new trainee a copy of MSFS 2004 with professional addon for the first plane you'd graduate for, and the better trainees used that to become familiar with plane - cause usually the largest previous plane they flew would be a small twin piston plane like Piper Seneca.

Airline pilots in the US need 1500 hours of flight time to earn their ATP (airline transport pilot) certificate.

For non-military pilots, most of those hours come from general aviation aircraft.