There are various types of interns. Few are as follows
1. A student as part of thier cirriculum (training)
2. A student for their project (final year)
3. Hiring for short term to assist in any process(graduate or post graduate or diploma holder
here there are two clauses, one is paid and other one is without pay. Any clauses is concern the company has the right to fix up the timng. It depends on the work they are going to do. You can fix thier timings depnds on thier work.
Procedure for hiring is simple, derive a JD for them and approach any college and this is right to hire students from any college because they will be approaching for thier final project which is for 4 months.
What we do is, we always ask them to adhere to our timings. But you can chose to fix timing based on a need. I suggest you to fix flexi timing for them, so that they will not waste thier time nor your's.