As for the contingency there is a "first right of refusal" for the other partners in the agreement... And, this is one of my "what if" questions...
The reality is, if it’s not 100% yours, this right here is where things get difficult. IF... you can’t live with things the way they are.
If you want to spend money on something and one person exercises their right of refusal, better be able to be happy with the airplane as-is.
That’s probably good advice even for a single owner. Life changes can mean things you wanted to do and planned to do, can’t happen.
We didn’t exactly push hard on the person but the co-owner who took a long term break (he will probably be back someday) had no use for a fancy IFR panel. The other two of us kinda wanted to upgrade but we both were fine with not. If someone can’t be fine with not doing something like that, they shouldn’t be in a co-ownership.
When he took his break we changed a couple of things. We paid off the loan on the aircraft because we both loathe debt, and we put in the GTN and the GTX because that’s the panel we both wanted to fly behind.
But we were quite fine with our old panel and could have waited until closer to the 2020 mandate and enjoyed the airplane in that configuration also. We had three older “steam gauge” guys and it didn’t bother us to the point where we’d force or twist the arm of our third co-owner too hard.
If there’s something about the airplane that will drive you bonkers if it’s not changed... you might not have complete control over that in a co-ownership. So you need to know how bonkers it will make you. Or if you can mitigate it yourself.
Example: On the loan thing. I just kept my share of the loan set aside in short term investments. If something came up where I needed out in a hurry, write a check and be gone. On the panel, heck, the stuff I grew up flying had much worse panels and I was playing with ForeFlight and built a Stratux to keep my gadget desires in check.
Maybe a better way to put it is this. If your co-ownership keeps a smile on your face, even if you’d have a slightly bigger smile if you did everything YOUR way, 100%... then it’s going to be fine. If the control issues make you not smile over stuff, buy without co-owners.
The unhappiest co-owners I’ve known were LOADED and didn’t buy their own single-ownership aircraft, and then had strong thoughts about what they wanted their airplane to be, that it wasn’t. They felt like they were arguing with their co-owners all the time.
If you don’t like what you’re buying, as-is or a solid agreement to change it before buying, don’t buy with co-owners. Or hunt for co-owners who want to do the same things.
A group of time builders buying an airplane for that vs long-haul airplane owners is another good example. Or a persnickety owner who wants every single squeak dealt with immediately vs someone who can let minor stuff go for s little while.
Just watch out for the clashes like that. Those will be the constant friction points that will rub someone raw and make them grumpy about co-ownerships.