I'm not sure what your question is, specifically, but here's the story:
Bill and Bob (not their real names) met in 2000 or shortly before because they happened to both be looking for a plane to co-own. They bought this plane in early 2000 and brought it to California. I have purchased Bill's 50% share of the plane from him, and Bob is staying on as co-owner. Bob and Bill used the AOPA sample co-ownership agreement as the basis for theirs, and Bob and I are doing the same.
Bill is also reinvesting $10,000 from what I paid him for his 50% share back into the plane, with the stipulation that the money be used exclusively for the engine overhaul. In exchange for doing that, he has been credited with 80 hours of flying at the dry-lease rate of $125 per hour. He has until 12/31/2020 to use up his 80 hours. (He's flown fewer than 10 hours total over the past two years, so I'm not expecting that he'll use all 80 hours he's paid for. But it's okay if he does, as the plane will be better off being flown more regularly.)
It's not in writing, but as soon as we have had the engine overhauled, probably sometime in the next few months, we will begin looking for a third co-owner to come in. With that person's investment we will upgrade the panel with some new avionics, and perhaps add or upgrade a few other things. What is already a very nice airplane will be superb!
I hope that answered your question; if it didn't, let me know.
Gerry