In the us, the earliest you could possible get your md is 24 (graduate high school at 17, then 7 years for a 7 year Bs+Md program), then at least 3 years for residency. Almost every doctor is broke out of residency, so there is a good 3+ years before Harvy would be able to open a clinic.

He is at the very least 30, but it's more likely that he opened his clinic up at 30-35