You can apply H1b at any time as long as you get J1 waiver.
But 1 year in J1 status is one of the minimun requirements for filing a waiver application, and the processing time of J1 waiver may last around 6 months to 1 years depends on your situation.
But 1 year in J1 status is one of the minimun requirements for filing a waiver application, and the processing time of J1 waiver may last around 6 months to 1 years depends on your situation.