collective are not meant to make credits , they can gain a great number from a populated plunder , OR they can produce credits from farming , remember each 1 unit of food produced will be multiplied by the selling price on the market , making it a better income than actually making credits , so agriculture or population / plunder are the 2 BEST paths to take for collective.
but a direct answer to your question is yes it is possible for all races to make + credits , its just unsuitable for some races such as Collective.