As an exchange student, you are usually exempted from any tuition fees at the partner university. Nevertheless, you may be required, for example, to show certain funds in advance as a guarantee (possibly through a sponsor). In non-European countries, this can be several thousand euros per semester. Other fees (such as application fees or administration fees) are not included in the tuition fee waiver and must be paid individually.
If you do not take a leave of absence for the duration of your semester abroad, you will continue to pay the regular semester fees at UPB. Make sure you remember to pay the semester fees within the re-enrolment period. If you take a leave of absence, you might have to pay a reduced amount. Further information is available at the UPB Service Center.