I just met someone yesterday who arrived very recently. She's here on a volunteer basis (church) and intends to stay for 3 months, with possibly a trip to Korea and back to extend the stay. She's young and doesn't have much money with her. I don't know what she said at immigration when trying to enter the country, but she said that they grilled her for over an hour in a separate room questioning how she could stay without having money or a job. However, they did finally let her in.

They'll be suspicious, but proper paperwork from the farm would probably go a long way to ease their fears.