Nikolaos, I'm not sure where you are, but at least in North America, the norm is for a bachelor's degree (4-5 years, however long it takes) and then to seminary. I believe Holy Cross is four years for the M.Div?
It's standard practice for Orthodox priests in North America to be both university AND seminary-educated. Some bishops will allow exceptions to that standard practice - for SEMINARY at least, but it's on a case-by-case basis, and up to the discretion of the bishop, and the Holy Synod he belongs to might have to weigh in on the decision, as well.
I know someone who immigrated to the US from a Orthodoxy country in his late teens. He never took any university courses for his bachelor's degree. He is now in his early 30s, married with a family. He is going through his diocese's diaconal vocations program to become a deacon, but before he can go to seminary he has to get his bachelor's degree, per our bishop.