I think there is a company in Sydney that did this also?
I have thought of doing this but being the provider and rotating pins around but haven't done the numbers, and then there is the lugging around and carrying up stairs etc.
I think $500 for 3 months sounds like a nice number ($41.50 a week) which is sort of equivalent to a new dvd rental at $6 a night for 7 nights, but this would take 3 years to pay a new Stern back at $6k new. Any more and doubt you would get any takers and less isn't worth it as you still need to consider service / parts cost and haulage. And if the person cancels before the the end of 3 months, it could be $200 a month.
But on the flip side would be a nice way to build up your collection.