I understand things are strapped but using the unpaid internship route - why didnt you just ask for middle/upper class kids with wealthy parents need apply only. IF you want work for free and truly wish to open yourselves up to gaining talent from all areas you should package up the position so it can be managed in spare time or weekends or even over the internet.
Only the priveleged may apply would have to be the caveat otherwise..
Bar the location preference so you can hunt them down and slay them if they mess up - I think I do all of the above (albeit badly and half arsed) for free anyway. But if I officialised it - it would count as a job therefore impacting tax etc zzzzzzzzzzzz.
TIP OF THE DAY – If you're being chased by a police dog, try not to go through a tunnel, then on to a little seesaw, then jump through a hoop of fire. They're trained for that.