The protestant church takes many forms. Some protestant churches don't have vicars but have lay preachers and ministers.
If you are referring to the Church of England, It takes three years of full time study at Theology College before you start your curacy which is 4 years 'on the job' training during which time you would take services, officiate at weddings, baptisms and funerals and eventually take a service of Holy Communion.
So a minimum of 8 years, so you would be at least 26 before you were a fully fledged vicar with your own church.