I have a co-ownership situation that worked.
When we were young, we really wanted a boat. So, we went to a boat show, my wife, me and my brother in law. We ended up with a brand new boat, owned 50/50 between us. We used the hell out of it, multiple fishing trips during the week at a local lake. 2 Annual week long vacations to larger lakes.
The boat lived at my house.
I maintained it.
We took all of our vacations together, used the boat together 100% of the time.
I was responsible for all the annual maintenance, winterizing, etc.
I towed it everywhere we went.
We shared all of those expenses 50/50.
It worked just fine. We still get along great to this day. But, as you can see, there was no "split time".
No...finger pointing, no doubts about who did what when, and no issues with the bills.
If that's the kinda relationship you have with your "partner", it might just work out.
If not......I agree with the others, it's a good way to lose a friend.