This seems to vary from operator to operator dependent upon equipment/company size and the type of flying that is to be done. It was my experience that the low end was right around $375.00 to $400.00 per flight day with the high end being in the range of $475.00 to $525.00 per flight day as contract. You may or may not be able to negotiate a better day rate. If you are looking for salary numbers and "averages" then I would suggest that you refer to the NBAA site and go from there. You may not necessarily be able to command "more pay" if you are checked out as a captain in more than one equipment type. Many operators limit how many different equipment types that you can be checked out as captain in due to insurance reqts. and limitations.
You may also want to call other operators in your area that operate similar equipment and see what they pay, atleast you will have a starting point.
good luck,
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