Heard a tale from several different sources, that impecunious 'Ab initio' to Commercial guys on straight through ciourses have rented themselves a nice 182 or similar and have gone on hours building trips around the US of A and all occupants have claimed the hours irrespective of their crew status!
I offer this as an anecdote but the sharing costs route might be just the way to go, eg sharing with 1 other gives you a rental rate of around $160 per hour that would seem to make it much more do-able. In the UK you could probably get a a 172 or similar on a block booking for less than that.
Good luck anyway!