In: Accounting
You can create a Double ledger accounting system either by using a specific accounting software or you can create excel system on your self.
Excel system is the most cost effcetive incase of any budget constraints. Also it is convinient for small businesses or individual. However it lacks control and getting historic data shall be difficult until unless you maintain the system in such a way as to get the whole historic data.
You may Prepare a Balance Sheet, Capital And Profit and Loss Account whereby you can give double entry impact in each ledger. You can assign a chart of accounts i.e. general Ledger No. to each account you want to maintain and while passing the entry in a separate sheet, you just need to assign the specific GL no. to it.
Regarding the Fixed and variable costs to verify profits for estimated job quote
You shall have to maintain a separate column to maintain if the cost is Fixed or variable and also assign such cost to each job to identify the fixed and variable cost
You can do this by creating separate excel or a specific Sotware like SAP, Oracle Tally etc shall help