Paperwork,
I think (GENERALLY), buying your own and renting it out, doesn't pay. I know a lot of owners (from single cab to major operators) who will tell you there is little or no money in it.
Where there is money, is in the add on bits, like:
renting out crews (pilots/crewmen, etc).
contract work (preferably government contracts).
maintenance.
refurbishing.
Work out how much it costs to keep your cabs, then translate that to how many hours you would need to rent it out for, per year to break even, and go from there. It might surprise you how many hours you need!
All the successful guys I'm aware of, dabble in the above list.
However, there are always exceptions to the rule:
I saw in one of Autorotates mags (I think), a guy in Aus who bought himself a Kawasaki 4 seater with floats and does tourist flying to the reef and outlying islands. He stated he made enough to 'relax comfortably', but the great thing about it was:
(a) the scenery
(b) the lack of pressure
(c) he was the boss!
Good luck................
