If a vice president takes over office how many years can he take over for and still run two more terms in office?

According to the 22nd Amendment, ratified in 1951, a succeeding vice-president who serves less than 2 years of a President's term is eligible to serve two full terms of his own, if elected. If the vice-president (or any successor) serves more than 2 years of an unexpired term, he/she is only eligible for one additional four-year term. Since this was not further addressed in the 25th Amendment (1967), the provisions remain in effect in the present day.