Highly unlikely you will keep the plane for 40 years. Practically
unheard of.

I would recommend buying a single, non-retract airplane that will carry
the load you need to carry. Cessna 172 or 182 or a Piper Warrior or
Pathfinder. Retractable gear is a maintenance headache. With your short
hops, speed doesn't really matter. I would also recommend buying it
with the avionics you want, although with 10K in shipping costs you may
have a hard time finding exactly whay you want in Hawaii.

As for leaseback, a simple plane like a 172 or Warrior will rent MUCH
more often and the required insurance premium and required 100 hour
inspections will dictate that you rent it as much as possible if you
want to have any hope at all of breaking even or better.

If I were in your shoes I would either get a 172 or a 182, one of the
later models (1999 or so), but not a new one. New airplanes depreciate
a LOT the first year, so I'd let someone else take that hit. However an
older model that has the avionics I want, if I can find it, would do
even better financially, but would not have the newer planes
reliability. If you prefer the Piper line, then choose one of those.

Good luck.