My first and last partnership was a bad experience. However, I don't believe that all partnerships are doomed, but careful concideration is key and i am interested in trying again. We shared a light twin and used thae standard AOPA aircraft partnership agreement.
I Partnered with a a 767 Capt. who worked for Continental Airlines ( first mistake). For a guy with a pretty reasonable paycheck, he was always broke at the end of the month. He had a lot of credit cards though. His trick was to continuously buy new things for the plane and submit the receipts in lieu of payment. Although this violated the partnership agreement, he decided to test the limits. A typical scenario would develop like this:
I would come to the hangar and discover that lots of money was spent to move the compass from the glare shield to a new mount on the top of the windscreen so he could put his GPS on the glare shield instead of yoke mounting it. Now, the original sunvisors wont fold down, so we got a new pair of Rosen visors. A stunt like this would about equal a month's share of insurance, hangar and airplane loan and he could put it on his credit card and just rack up more debt.
The straw that broke the camel's back resulted in an emergency landing after he performed some maintenance on the right engine prop spinner. Apparently all the screws were put in and not fully tightened when he went to lunch. They were never tightened when he returned and my preflight didn't catch it.
The spinner started coming apart in flight. Once I returned, he blamed me for the damage for not preflighting the plane well enough.
While I will never preflight a plane without being absolutely sure that the screws on the spinner are all tightly fastened, I contend that he should never have removed the spinner and returned the plane to service since he is not an A&P (not the only time that he would tinker with shit that requires an airman's cert that he didnt have.)
I tried to sack him for another partner, but he liked being broke so I sold my half to him. I lost a little money on unrequired maintenece and airplane gadgets ,but got the full share of the plane. He partnered with two others and that disolved quickly. They now have the plane.
Ultimately it comes down to this: Be sure there are no lose screws (goes for partners and spinners) before committing. Don't partner with seemingly rich broke people. I think that in my mind, I assumed that his being a 767 pilot would somehow add value to partnership (bad assumption). It actually made things worse as he had no real practical GA airplane ownership and flying erxperience (it aint like the airlines).