So my son is coming for an internship. He will apply for the ED visa which is 3 months, but the internship is 6 months

I understand he needs to show a return ticket, but on which date, after 3 months or after 6 months?

Is there a company that shows reservations but not bookings?

I know I can buy a cheap budget airline ticket to wherever......

If he has a  non-ed visa when entering the country a return or onward ticket is not required.