In the long term, I'm planning on getting into a partnership on a single engine
plane capable of carriyng 4 adults + luggage for a 500 mile trip. Before I get
all the way into a partial ownership situation, I'd really like to spend some
time flying some of the potential aircraft I'm interested in, to see if they
really match what I'm looking for.

Since the short list of planes is: A-36 Bonanza, Cessna 210, and Piper
Saratoga; I'm not able to find them available for rental anywhere nearby (very
few FBOs rent these anyway). I was thinking of trying to find a local (Toledo,
OH; Detroit, MI, or Ann Arbor, MI) owner with an under-utilized plane, who is
willing to lease time on their plane for 4-6 months so I could use it for some
trips totalling 40-60 hours. My questions to the group a has anyone done
something like this, and what are the potential pitfalls (insurance, liability,
availability, etc...) that I should be concerned with?

I'm Commercial, Instrument, Single Engine rated with 500+ hours and 100+
complex, 100+ high perf so I'm assuming that becoming a named-insured pilot on
the policy won't be much of an issue after a 5 hour checkout.

Thanks in advance,
Eric