Do not let the operator own the aircraft - they should be owned by a separate company then leased to the operator. This would be for liability purposes.
The magic number to break even is around 500 revenue hours per year.
This may help you establish a breakeven point:
In looking at costs per type you need to be looking into things like costs per seat mile.
Also, most important:
There is no such thing as a cheap helicopter!
Which applies to maintenance as well; if you save money one year, expect to spend it the next, in which case, be wary of buying machines with low hours - very often the maintenance will not have been kept up to date and it will be easier to buy a new engine.