Resource Codes & Cost accounts

Haresh,
Resource Code is the same as Activity Code but more resources specific grouping like, company grouping, crews grouping, specialty grouping, skills grouping etc…

Cost Account is commonly used in Cost control management and EVM.
It is a management control point at which budgets (resource plans) and actual costs are accumulated and compared to EV for management control purposes. A cost account is a natural management point for planning and control since it represents the work assigned to one responsible organizational element on one program WBS element
Below are some links for your reference:
Cost Control, Monitoring and Accounting
Project Cost Control: The Way it Works
IS THE EARNED-VALUE METHOD AN ENEMY OF WORK FLOW?
Technical Managers Earned Value Management User’s Guide

Keep as many cost code groups as required, you might need a cost code set for your company Job Costing using same cost accounts across all your jobs while you migh need a particular cost coding set for every job BOQ as per the Owner requirements.