1hraman, I was was in a co-ownership in an airplane for 15 years. Partner and I had use for plane for one week and I had the next one. If I needed it for his week, and he had no plans for use, I called and got it, and same with him. We flew about the same hours per year, so maintance was split. As per agreement, it was refueled after each flight.
We bought the plane in 1986 for $28 thousand and flew it for 15 hundred hours and sold in 2003 for 53 thousand. We never had no problems and partnersh worked out great for both.