Ok, I have an example for you guys to poke holes in, but imagine a 3 way shared ownership situation on the following piper cherokee 180:
http://www.controller.com/listingsdetail/aircraft-for-sale/PIPER-CHEROKEE-180/1963-PIPER-CHEROKEE-180/1318485.htm
sale price is $36,900 (I've seen several in the 30K to 40K range that look decent, so this seems like a good example). Each person comes to the table with a 15% downpayment of $1,845. That makes a financed amount of $31,365 on a 15 year note at 6.5%, which is $273.22. Split 3 ways its $91 per month for the loan payment. Several people have given figures of $100 a month for insurance, plus $100 a month for a tie-down, but since I'm a low hour pilot, we'll go with $150 for the insurance piece. Add in the the cost of an estimated $2000 annual, and that's $417 per month, split 3 ways is $139. On top of that, throw in $55 per month per person to cover the eventual engine overhaul. That comes out to $285 per person, per month, fixed costs.
So then, take $15 per hour for incidental maintenance, plus fuel in my area at $6.00 per gallon. with a fuel burn of 10 gallons per hour, a total of $75 / hr.
After a year, you'd have $6230 in reserves to cover the annual (this assumes each person flew 50 hours over the course of the year), and any maintenance that's required, and also the savings for the eventual overhaul is included in that figure. This also would provide a buffer in case something a bit more pricey goes wrong, at which point we could adjust the monthly costs accordingly to cover the eventual overhaul, or sell if it if we start to get worried about long-term costs.
Also, as others have pointed out, you could fly this 150 hours per year for 5 or 6 years and then sell it and upgrade or do whatever, without ever performing the overhaul.
Ok, I think these figures are pretty conservative, but y'all tell me what I'm not taking into account? I'm sure someone will think these figures are totally bogus..