I recall them talking about adding co-ownership functionality, but I have no idea where that sits on their to-do list.

I'm fine with proceeding along the lines you lay out. If we get a few months down the road and there's no mechanism for co-ownership and you find you don't have the time you'd like to invest in the territory, then I'll happily take over.

From there, once they do implement co-ownership, we can revisit the idea.

FWIW, if we split an outright buy, I think my attitude would be that any effort either of us invests is purely voluntary, since we would both have the option of sitting back and treating the territory as a passive income source. I appreciate the concern, though, about getting into an arrangement like that with someone you only know online.