Very very important. As is leaving the family back home. The guest worker should be allowed to stay 3 or 4 months max --- enough time for harvest season or a short-term project --- then back home.
Or else the whole family shows up anyway as illegals, which is the case now for both illegals and legal "temporary" workers.
The whole damn thing is an unworkable pipe dream, dependent on non-existent enforcement. Remember when employer sanctions were going to solve the whole problem?