I'd charge $100 just to get the crap off the belly of half those flying school junkers!
To clean and detail a Baron used to take me at least 3 hours, usually a whole morning or afternoon.
A PA31 used to take up to a whole day sweating in the sun.
Scarecans and 210's a good morning or afternoon also.
Have fun!
(I notice you are in Darwin?? if you clean a D*****Air aeroplane, make sure you charge up front else you will not be paid!!)