Cost control documents
The Cost Breakdown Structure CBS extends the WBS, that only has estimates for the cost of labor, by adding the costs of material and resources.
The Work Breakdown Structure has a complete list of all the tasks to be performed and should be the starting point for any serious estimation effort.
As you have the tasks durations you can easily estimate the cost of labor by devising a unitary (daily or weekly) cost to each individual listed as the responsible person/entity. In addition to labor, consider the materials (eg. paint or mortar) needed to complete each task.
Finally, estimate the cost of any additional resources (eg. a crane, a laboratory) needed for the task. In data network projects you might consider building a live test environment to test your solution without disrupting the production network. This lab could be composed of rented equipment that would have their cost assigned to a task in the WBS.
This is a bottom-up estimation technique starting at the lowest level and going up.
The Budget is another document that contains financial data but is organized by milestones with date and the amount to be paid at that moment. The level of detail is reduced and the payments are aggregated by date to make it easy to insert the planned payments in the organization cash flow.
The Budget contains the best overall estimate using task estimates from the CBS and adding two types of reserves: contingency reserves and management reserves. The total overall estimate of the project is found in the budget.
