I went through this a while back with my RV-12. It's now in an LLC, with each of us equal owners of the LLC. That gives us several advantages:
- The flexibility to add and remove owners and airplanes, if we decide to do so
- Ease of our spouses dealing with disposing of the ownership interest if one of us croaks unexpectedly
- Spells out in detail how things are handled -- sale, relocation, death, overhauls, upgrades, etc.
We have an operating agreement that covers how we fly, responsibilities for maintenance and cleaning, scheduling, etc. I pulled sample agreements from AOPA, a Beech forum, and one or two others. We made some minor and a few more substantial changes to meet our needs. Once we had it about where we wanted it, we brought in an attorney to do the final cleanup, look it over, bring up a few questions we hadn't thought of yet, etc. The whole thing cost us maybe 1 AMU to complete.
I think the most important part of the whole exercise was done well before we even started on the paperwork. We talked, a lot, to make sure that our personalities, expectations, and use patterns were compatible. So far we haven't had any scheduling conflicts or disagreements over maintenance or upgrades. We each contribute a fixed monthly amount to cover the hangar, insurance, and time-sensitive maintenance (transponder checks, ELT batteries, etc.). We arrived an an hourly wet rate that includes an overhaul reserve, and deduct what we spend on gas.
So far, so good. I'm flying more and spending less per hour. And I agree, make sure everything is agreed upon and spelled out on paper. If there are conflicts, they will likely not come up short term -- just later on, when memories of what was agreed upon can get fuzzy. Make sure it's all documented and signed.