Our four partnership works great.
1. Monthly membership $80.00 to pay for hangar, condition inspection, insurance, periodic maintenance (mostly oil changes.)
2. Engine fund that stays with the plane ($5.00 a tach hr.)
3. Special assessment when we as a group decide to add something to the plane, and when the monthly membership cannot pay all of the items that need corrected that are found during the condition inspection.
Each of the members have a different flying routine; one is a dawn patrol guy, another partner who generally cannot fly except on the week-end, one that is not a morning person and can't get to the airport until later in the day, and another who is very flexible about flying time. Seldom any conflicts.
Pilots top off the fuel after each flight at the individual pilot's expense; oil is added if needed before each flight and is charged to the monthly fee, not to individual pilots. We fly 200 hours total each year, and about equally (50 hrs) for each partner.
We set up an LLC, got the checking account for monthly membership, and a saving account for the engine fund.
We did agree to designate only one person who talks to the mechanic and schedules work and what we want done. We also designated only one person who writes checks and pays the bills (not the same person who talks to the mechanic.)
We're five years into this partnership, and it is working fine. Cost each partner about $3000.00 a year. Very reasonable.