Thanks a lot for answer!
I misunderstood the wording in the contract. Yes, tickets within VAC network are free (except ticket tax as far as I understood). So it will just be the accomodation over there where screening takes place. And this will be paid back by agency after successful check.
Ok, so this salary will be the value with which I can count, there won't be any xx% subtracted. That's nice to hear.
I will have to find out how to keep peace with my home tax system.
But step by step. First I will have to pass screening, then the next step. Thanks for answer!