One usually starts with nothing -- but this represents high earnings! (9,6)
I believe the answer is:
telephone number
I believe this clue is a double definition.
'one usually starts with nothing' is the first definition.
(most telephone numbers start with zero)
'this represents high earnings' is the second definition.
(a large sum may be called a telephone number)
'but' is the link.
(Other definitions for telephone number that I've seen before include "that may be kept in cell" , "Very large figure" .)