You wouldn't build without architectural plans, right? So why would you build without a cost plan or building cost estimates?
Right from early design stages, it is critical that you get cost advice on what the potential construction cost of your development is. This will allow you to make design decision early without having your architect start from scratch if it is over-budget.
The process of cost planning involves preparing building cost estimates and revisiting those estimates at regular intervals to ensure you are still on budget. It can begin right when you first have an idea and continue right through to project completion.