How common are aircraft partnerships compared to outright ownerships?

I've come to the point where I'm looking to get into owning an
aircraft. However, I've read (and calculated) that the break-even
point for owning comes after about 150-200 hours per year.

I'm not going to be doing nearly that amount of flying. In fact, I
don't know anybody other than a CFI or some other commercial pilot who
would. So, it seems that a partnership would be "the way to go" for
most people who want to vacation or take extended trips with an
aircraft.

If so, however, how come they're so *hard* to find? I don't see any
listed in trade-a-plane or on any aircraft commerce sites like
mooneymart or whatnot.

Based upon the number of listings that I've come across, partnerships
are downright endangered species.

Are they? And, if not, how do I go about *finding* them?

- Joe